: P0420 Code



STSMAN
12-30-05, 07:02 PM
Ok my car kept throwing the P0420. After futher investigation I found out that the CAT O2 sensor was bad. I replaced it. But didn;t reset the code yet. My question is do I reset the codes or will it reset itself with a few drive cycles?? if I remember correctly that code will not reset right away unless you clear it manually. Is my memory serving me well ?? :D

Eldyfig
12-30-05, 07:16 PM
Yes, it does serve you well. Even when a code is posted, the PCM still tests that particular sensor. When the sensor gives passing parameters, the code will remain in history for a particular number of ignition cycles before it disappears.

mcowden
12-30-05, 07:35 PM
Yes, it does serve you well. Even when a code is posted, the PCM still tests that particular sensor. When the sensor gives passing parameters, the code will remain in history for a particular number of ignition cycles before it disappears.

Exactly as Eldyfig said, the code will stay in memory as a "history" code, meaning that the code happened in the past and is not currently a problem. It won't hurt anything to leave the code in there. As long as the sensor is replaced, you are back to normal.

STSMAN
12-30-05, 08:11 PM
Exactly as Eldyfig said, the code will stay in memory as a "history" code, meaning that the code happened in the past and is not currently a problem. It won't hurt anything to leave the code in there. As long as the sensor is replaced, you are back to normal.

I understand about the code in history, ,however what about the MIL light?? Will it clear after a few drive cycles?? It should clear when that code becomes a history code.

mcowden
12-30-05, 09:50 PM
I understand about the code in history, ,however what about the MIL light?? Will it clear after a few drive cycles?? It should clear when that code becomes a history code.

If the SES light is still on, you may have a CURRENT code in there in addition to the HISTORY P0420. Have you checked for codes in every category, or just waited for all of the categories to scroll by? If there are no other codes, then clearing the P0420 will snuff the SES light. If you do find another code, let us know so we can help you figure it out.

STSMAN
12-30-05, 10:18 PM
If the SES light is still on, you may have a CURRENT code in there in addition to the HISTORY P0420. Have you checked for codes in every category, or just waited for all of the categories to scroll by? If there are no other codes, then clearing the P0420 will snuff the SES light. If you do find another code, let us know so we can help you figure it out.

no just the current P0420 code.. but mind you I just repaired the car today.
I need to complete more drive or ignition cycles. The light should go out after 3 of these cycles, we will see.

Thanks for the help

mcowden
12-30-05, 10:23 PM
no just the current P0420 code.. but mind you I just repaired the car today.
I need to complete more drive or ignition cycles. The light should go out after 3 of these cycles, we will see.

Thanks for the help

Actually I just looked up the P0420 code and it means "Catalyst System Low Efficiency," which means that the catalytic converter isn't working as it should. Which O2 sensor did you replace? The one before or after the converter? It's possible that the converter is bad and will need to be replaced to make the SES go away. If the code still shows up as CURRENT, the problem is still happening.

Ranger
12-30-05, 10:27 PM
If you do not clear it, it will extinguish the MIL and go into history after 3 ignition cycles with no fault detected. It will then go into, and stay in, history for 50 ignition cycles, after which it will be deleted.

ewill3rd
12-31-05, 07:53 AM
You'll probably be looking at that light for awhile unless you clear it.
As Ranger said it must pass the diagnostic test 3 times before the light will go out. The catalyst monitor test might not run every time, in fact it may actually rarely run.

Problem number two is... a bad O2 sensor will not set a P0420. A bad O2 sensor will set a bad O2 sensor code. P0420 indicates that the O2 sensors are in fact good and the catalyst is not doing it's job. The O2 sensor diagnostic tests MUST pass before the P0420 DTC diagnostic will even run. If the PCM knows the O2 sensors are operating properly and the test enable criteria are met the P0420 test will run.


These conditions must be met in order for the diagnostic to run:

No TP sensor, MAF sensor, MAP sensor, IAT sensor, ECT sensor, HO2S, HO2S Heater, Fuel trim, Misfire, EVAP System, EVAP Control, VSS, or Idle Speed DTCs are set.

• Engine speed since end of last idle period is more than 800 RPM for 46 seconds.

• Idle period is less than 180 seconds (3 minutes).

• Actual engine speed is within 100 RPM of desired engine speed (Non-California)

• Actual engine speed is within 125 RPM of desired engine speed (California).

• Engine run time is more than 7.5 minutes.

• The predicted catalyst temperature is between 420°C and 650°C (788°F and 1202°F).

• BARO is more than 75 kPa.

• ECT is between 71°C (160°F) and 120°C (248°F).

• IAT is above -6°C (21°F).

• Engine is in closed loop fuel control.

• Tests attempted this ignition cycle is less than 12.

• Test attempted during idle period is less than 1.



Here are the conditions for the code to clear or the MIL to go off:


The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.

• The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• The DTC can be cleared by using the scan tool Clear DTC Information function.




HTH

prcouture
05-31-08, 03:44 PM
Read these details and had the cat replaced on my '00 Deville after the P0420 code came on. Code returned! Is it possible one of the O2 sensors crapped out when the cat was bad? Curious if anyone had success fixing the P0420 code with a replaced O2 sensor.
Thanks

krimson_cardnal
05-31-08, 03:56 PM
prcouture - Re-read what ewill just posted carefully. P0420 is not an O2 sensor code. In fact if thrown it means the O2's are good. K_C

Submariner409
05-31-08, 03:58 PM
eWill3rd posted that ^^ 2 1/2 years ago...........I believe that you have an after-cat O2 sensor which monitors the after-cat oxygen content, a measure of cat efficiency. If that sensor was removed and replaced during the cat exchange it's entirely possible that an 8 year old wire, subject to some intense heat, has let go. The instructions for that sensor also caution about bending one of the wires which carries a "clean air reference" signal. That after-cat sensor can be found at Lindsay Cadillac over there >>>>> (Parts, Luke) or www.rockauto.com (http://www.rockauto.com). It is a plug & play item, up on a lift.

krimson_cardnal
05-31-08, 03:59 PM
prcouture Reread what ewill posted carefully. A P0420 code being thrown actually means the O2's are good. A bad O2 will throw an O2 code. K_C

oops - didn't mean to say that again - looks like sub and me crossed paths

AJxtcman
05-31-08, 05:55 PM
Read these details and had the cat replaced on my '00 Deville after the P0420 code came on. Code returned! Is it possible one of the O2 sensors crapped out when the cat was bad? Curious if anyone had success fixing the P0420 code with a replaced O2 sensor.
Thanks

Hmmmmmmmmmmmmmmmmmm :tisk:

First off did you have a GM converter installed?
Was it one of those aftermarket converters that is 1/2 the size?

The GM catalytic converter, P/N 25755681

Some will also require a new software calibration to keep the converter from failing again!


New calibration to correct the EST control circuit in the PCM from turning off spark intermittently, which causes misfire events, possibly damaging the catalytic converter, as indicated by DTC P0420. Improved EVAP diagnostics and correction for Mode 6.

ewill3rd
06-01-08, 10:44 AM
If you bought an aftermarket cat, take the car back and have them install the right one.
Legally they have to provide you with one that will do the job the GM one did. Many aftermarket ones have trouble meeting the requirements to pass the on board diagnostic tests... which means they don't work.

1stkobefan
06-29-08, 10:17 PM
If you bought an aftermarket cat, take the car back and have them install the right one.
Legally they have to provide you with one that will do the job the GM one did. Many aftermarket ones have trouble meeting the requirements to pass the on board diagnostic tests... which means they don't work.

Who are "They" cuz I recently bought an 02' DTS that's got an aftermarket Cat & I just can't afford the $900+ it cost to replace it with the GM factory Cat. I just had the Cat replaced & the SEL came back on 3 days after I had it replaced. Plz HELP.
Also where are the spark plugs located on the 02' DTS. Thanks.

Submariner409
06-29-08, 10:26 PM
You'll have to fight out the cat with the selling dealer. If the SES light was on when you bought the car, I have no idea of your recourse. The Northstar series of FWD cars hates aftermarket cats: they supply nothing in the way of reduced restriction (there isn't any to speak of) and almost always seem to cause DTC problems.

The spark plugs are down in wells inside each cam cover, connected by conductive boots to each of 8 coils in the pack cassettes which are set into the cam cover tops. The cylinder heads are technically 4-valve semi-hemi (penthouse) units with the spark plug in the center of the 4 valve array. The plugs are ACDelco 41-987 Double Platinum units (ONLY) and can be obtained from one of several outlets used by most of the CF members: It's all in here and Seville/Deville. 100,000 mile replacement.

(retired QMCM (SS) (DV) COB, all subs)

1stkobefan
06-30-08, 12:36 AM
You'll have to fight out the cat with the selling dealer. If the SES light was on when you bought the car, I have no idea of your recourse. The Northstar series of FWD cars hates aftermarket cats: they supply nothing in the way of reduced restriction (there isn't any to speak of) and almost always seem to cause DTC problems.

The spark plugs are down in wells inside each cam cover, connected by conductive boots to each of 8 coils in the pack cassettes which are set into the cam cover tops. The cylinder heads are technically 4-valve semi-hemi (penthouse) units with the spark plug in the center of the 4 valve array. The plugs are ACDelco 41-987 Double Platinum units (ONLY) and can be obtained from one of several outlets used by most of the CF members: It's all in here and Seville/Deville. 100,000 mile replacement.

(retired QMCM (SS) (DV) COB, all subs)
So these are the only plugs i can use? Cuz I bought 8 of the Bosch Platinum 4. So would u suggest me trying to change them myself or just pay to let a shop do it. The front seems easy but the back would be near impossible. Thanks for sharing the knowledge.

ewill3rd
06-30-08, 07:32 AM
Two pieces of advice.

#1. Don't use Bosch platinum plugs in a GM engine. They won't run right and it may even cause some real drivability issues for you. Look over the forums and read the stories about how people had poor running cars until they put stock plugs back in.

#2. If you don't know where the spark plugs are, I'd recommend you pay someone to put them in. It could be expensive depending on where you live but it might keep you from running into some potentially serious problems.

AJxtcman
06-30-08, 09:27 AM
Two pieces of advice.

#1. Don't use Bosch platinum plugs in a GM engine. They won't run right and it may even cause some real drivability issues for you. Look over the forums and read the stories about how people had poor running cars until they put stock plugs back in.

#2. If you don't know where the spark plugs are, I'd recommend you pay someone to put them in. It could be expensive depending on where you live but it might keep you from running into some potentially serious problems.

I second that

I had a coworker about 10 years ago that had a 67 Camaro (not stock) that ran 12 second 1/4's. He had Bosch Platinum plugs in it. He put them in every car he or his family member had. I informed him that the Bosch plug was not the best for his application.
We did a test.
He pulled the plug and installed AC Delco Rapid Fire plugs. This plug is very similar to the AC Delco Platinum or Iridium plug.
He ran a quicker time at the track and he said that he had better throttle response.

The Bosch plugs he removed had buildup on the porcelain portion of the plug. The design of the plug will allow for this type of build up. A Northstar can burn oil. The mix of those two will lead to a possible misfire or weak spark.

I was a drivability tech for about 7 of my first 12 years. I didn't have a hoist most of the times. I have changed a lot of spark plugs and I can tell you that the Bosch Platinums are on the bottom of my list. I have seen a lot of gimmick plugs over the last 22+ years and them and Split Fires are at the bottom.

ewill3rd
06-30-08, 09:33 AM
Oh and for the guy above, the installer is required to warranty the part for like 5 years or something, you can find more information on EPA regulations regarding converters online.
If you know where the cat was put on, take it back and have them replace it until the light stays off, the law requires them to do just that.
If they put a catalyst on that doesn't do the job that the original did they are in violation of Federal Law.

1stkobefan
07-02-08, 07:07 PM
Oh and for the guy above, the installer is required to warranty the part for like 5 years or something, you can find more information on EPA regulations regarding converters online.
If you know where the cat was put on, take it back and have them replace it until the light stays off, the law requires them to do just that.
If they put a catalyst on that doesn't do the job that the original did they are in violation of Federal Law.

So if the dealer sold it to me like this are they liable? If i change the O2 sensors to universal also, will that make it read within limits u think? Thanks every1 for the sparkplugs tips.

AJxtcman
07-02-08, 08:46 PM
So if the dealer sold it to me like this are they liable? If i change the O2 sensors to universal also, will that make it read within limits u think? Thanks every1 for the sparkplugs tips.

If the O2 sensor was the problem it would set an O2 Sensor code.

P0420 is a code that states that the post converter O2 sensor is switching at a similar rate and or voltage as the manifold O2 sensor.

Basically the post O2 need to switch at a slower rate by X% and the peaks in voltage need to be X% less.
Just say the cross counts need to be 25% of the Manifold O2 and the voltage swing needs to be no more than 20% of the Manifold O2.

A P0420 will set when both O2 are switching at the same rate and the same voltage.

ewill3rd
07-02-08, 10:13 PM
As to whether or not the dealer is liable, that depends on the laws in your state.
You might contact your local highway patrol office and see if they have someone that can specifically answer your questions.
If you didn't buy the cat you might have some issues... mainly just the expense of fixing it right yourself.
It could get someone up the chain in trouble for putting a substandard emissions part on the car.
The law actually requires a pretty long paper trail, but as I said there can be variances from state to state.

90devilleguy
07-16-08, 05:43 PM
Hey Guys, i'm having a problem lately and i wanted some feedback on the same code that is popping up on my car.

Recently i had the Front Cyl. Coil Cassette Pack go on my 2002 SLS. I replace the Pack and put new Delco Platinums that are the OEM plug #. I have since the repair gotten twice the PO420 Code. I will go and clear it and it came back a few days later. First time it happened i was on a long car ride. Second time was on the way home from work.

I seem to think that if my car was run under this bad misfire condition that this will cause the code to come up, right?

Should i just give it some more time and see if it keeps coming up? Or should i get a new Cat.....

Car only has 59,000 on the clock. Would the GM Emissions warranty cover this problem???

ewill3rd
07-16-08, 10:30 PM
The coil failure may have damaged the cat. It shouldn't take long after repair for the cat to clear out.
It takes a certain set of driving conditions for the test to run, not surprised it doesn't happen often.

I'd take it in and have them look at it, you'll probably need one replaced.

I woudl run the VIN to be sure but on most cars the cats and ECM are 8/80 coverage.

90devilleguy
08-28-08, 11:44 PM
The coil failure may have damaged the cat. It shouldn't take long after repair for the cat to clear out.
It takes a certain set of driving conditions for the test to run, not surprised it doesn't happen often.

I'd take it in and have them look at it, you'll probably need one replaced.

I woudl run the VIN to be sure but on most cars the cats and ECM are 8/80 coverage.

hey guys i'm finally getting annoyed with the SES light coming on again and again. I'm gonna take it to the dealer. The car is under warranty for emissions equipment still.

I have a question about dealing with the dealership. Do they have to do diagnostics on the car first before considering it's the cat? I really don't want to get stuck paying for anything else. cause i can go to a shop of my own and get other things that could be broken done cheap. I'm only taking it to the dealer cause i seriously feel it's a cat issue and it's covered under warranty.

Any feedback would be great.

Ranger
08-29-08, 12:04 AM
Tell them not to touch anything that is not covered.

ewill3rd
08-29-08, 10:42 PM
They can't do anything (in most states) without your prior approval.
They might ask for authorization on some checkout time up front in case it isn't a covered repair and you should only be responsible for what you agree to ahead of time.
It can be a pretty weird thing depending on the advisor you get. Most will prep you for some expense, they cannot just go on and on and check it all out and then try to charge you.

They can't spend your money without your authorization, make sure to ask them each time specifically what the costs will be as you progress through your visit. Make them be clear and concise, make sure they understand if you don't agree to it beforehand you aren't paying for it.

90devilleguy
09-02-08, 08:40 PM
I just was looking on GM Parts Direct and they list that for the cat converter and the rest of the exhaust behind it is sold as a kit for 1200 bucks?????

If the dealer has to replace the cat can they just replace the cat or do they have to replace the entire exhaust system????

Ranger
09-02-08, 09:22 PM
Salvaging the rest of a rusty system is IFFY. Chances are they will not try and require the rest to be replaced. You can see what they say based on the condition.

90devilleguy
09-02-08, 09:35 PM
see this is a small problem.....I have aftermarket mufflers installed on this car. If they replace the whole exhaust then they better give me those back.

Submariner409
09-02-08, 09:55 PM
The GM part number for a replacement exhaust system for a 2002 STS is for the whole thing.........cat to tips. Close to $1500 now, MSRP. All one piece, and the shipping is incredible......

Ur7x
09-03-08, 12:49 AM
I just was looking on GM Parts Direct and they list that for the cat converter and the rest of the exhaust behind it is sold as a kit for 1200 bucks?????

If the dealer has to replace the cat can they just replace the cat or do they have to replace the entire exhaust system????

2002 was a VERY bad year at GM for cats LOTS of failure across ALL car lines ... ONE TSB after another on this issue...

My 2002 STS had the cat die at 70,000 miles while still on the Federal warranty... The GM replacement cat is not a "complete" unit... It is a cut and clamp replacement. Nice :rolleyes:

If you have a P0420 code and you have 2002 GM anything you have a bad cat. Ask your parts guy for the TSB replacement part for your car if you must have OEM (expect ~500-800) for just the cat... Cut and clamp.

If mine were to fail off warranty it would be in line for an aftermarket one... "quality" "factory fit" aftermarket cats go for 80-160.. You can replace that cat about 5-10 time... I'm sure that GM has fixed the issues with the 2002 cats.. but I'm still nervous about mine and it hangs down about 2" lower then the "original" one.

AJxtcman
09-03-08, 01:16 AM
Important:

DO NOT REPLACE the following complete exhaust systems when replacing the catalytic converter.
25727006

88959335

88959334

25727009

25709529

Ensure the catalytic converter heat shield is upward. The "honeycomb" side faces downward.

New catalytic converter, P/N 25755681
GM LIST: $470.61

New exhaust seal, P/N 03544534

Nuts, P/N 11517031

90devilleguy
09-03-08, 11:24 AM
AJ- your basically saying that they don't need to replace all the components?

Ur7x- do you have access to the TSBs regarding this issue?

Let me know please. In case i need ammo for the dealership.

90devilleguy
09-03-08, 02:19 PM
Looks like it's the Cat.

Stealership is going to replace the Cat but they are trying to charge me the Diagnostics fee. I'm fighting it. I called Caddy Customer Service and hopefully they can work it out with the stealership. :)

derone
09-03-08, 04:17 PM
[QUOTE=AJxtcman;1623123]Important:
New catalytic converter, P/N 25755681
GM LIST: $470.61




That part has been replaced by a new part number.
GM PART # 19152013
CATEGORY: Catalytic Converter
GM LIST: $924.02

90devilleguy
09-03-08, 04:19 PM
[QUOTE=AJxtcman;1623123]Important:
New catalytic converter, P/N 25755681
GM LIST: $470.61




That part has been replaced by a new part number.
GM PART # 19152013
CATEGORY: Catalytic Converter
GM LIST: $924.02


Wow i'm glad i don't have to pay that!!!!!

Ur7x
09-03-08, 04:36 PM
Looks like it's the Cat.

Stealership is going to replace the Cat but they are trying to charge me the Diagnostics fee. I'm fighting it. I called Caddy Customer Service and hopefully they can work it out with the stealership. :)


It is ALL covered under the waranty... including the diagnostic fee

TSB:
Service Engine Soon (SES) Light On, Reduced Vehicle Power/Acceleration/Speed, Diagnostic Trouble Code (DTC) P0420 (Diagnosis and Replace Catalytic Converter) #03-06-04-028 - (May 15, 2003)

Service Engine Soon (SES) Light on, Reduced Vehicle Power/Acceleration/Speed, Diagnostic Trouble Code (DTC) P0420 (Diagnosis and Replace Catalytic Converter)
2002-2003 Cadillac DeVille, Seville
Condition

Some customers may comment of the SES light on and/or possible reduced vehicle power, acceleration and reduced top speed. DTC P0420 may be set.
Cause

The catalytic converter efficiency may be too low and/or restricted.
Correction


Follow the service procedure below for catalytic converter diagnosis and replacement .
<LI type=1>For diagnostic information, refer to DTC P0420 SI Document ID #792317 <LI type=1>Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle SI Document ID #377101.
Caution



In order to avoid being burned, do not service the exhaust system while it is still hot. Service the system when it is cool.
Always wear protective goggles and gloves when removing exhaust parts as falling rust and sharp edges from worn exhaust components could result in serious personal injury.

<LI type=1>Support the exhaust system near the resonator with a suitable adjustable jack.
<LI type=1>Remove the 4 nuts securing the catalytic converter to the rear exhaust manifold pipe.
<LI type=1>Remove the 2 bolts securing the center exhaust hangers to the rear suspension support brackets. <LI type=1>Remove the catalytic converter from the rear exhaust manifold pipe. <LI type=1>Remove the catalytic converter gasket and discard the gasket.
Important

Use care not to overextend the heated oxygen sensor pigtail.

<LI type=1>Lower the exhaust system with the adjustable jack to allow clearance for the cut-off tool.

Important

Ensure the cut is made on the catalytic converter side of the pipe.

<LI type=1>Cut (2) the catalytic converter (3) from the resonator inlet pipe (1) ahead of the step but as close to the step as the tool will permit. <LI type=1>Remove and properly discard the catalytic converter.
Important


<LI type=a>DO NOT REPLACE the following complete exhaust systems when replacing the catalytic converter.

25727006
88959335
88959334
25727009
25709529

Ensure the catalytic converter heat shield is upward. The "honeycomb" side faces downward.


<LI type=1>Slide the new catalytic converter, P/N 25755681, onto the resonator inlet pipe until it is fully seated against the heated oxygen sensor boss. <LI type=1>Install a new exhaust seal, P/N 03544534, on the four studs. <LI type=1>Install the converter onto the rear exhaust manifold pipe. <LI type=1>Install the four nuts securing the catalytic converter to the rear exhaust manifold pipe. <LI type=1>Install the 2 bolts securing the center exhaust hangers to the rear suspension support brackets. Tighten
<LI type=a>Tighten the catalytic converter nuts in a crisscross pattern to 25 Nm (18 lb ft).
Tighten the center exhaust hanger bolts to 30 Nm (22 lb ft).
Important

Ensure the catalytic converter outlet pipe is fully seated against the heated oxygen sensor boss.

<LI type=1>Install two exhaust clamps, P/N 15992529, on the converter pipe with the two clamp ends 180 degrees from each other. Each set of clamp nuts should face opposite directions for proper sealing. Tighten Tighten the service clamp nuts to 30 Nm(22 lb ft),
<LI type=1>Remove the adjustable jack stand.
Lower the vehicle and inspect for exhaust leaks.
Parts Information

Part Number
Description
Qty
25755681
Catalytic Converter
1
11517031
Nut (Only Order As Needed)
4
03544534
Gasket, Catalytic Converter
1
15992529
Clamp
2

Parts are currently available from GMSPO.
Warranty Information

For vehicles repaired under warranty, use:
Labor Operation
Description
Labor Time
L2300
Catalytic Converter Replacement
0.5 hr
Add A
Diagnosis Time
0.0 -- 0.3 hr

90devilleguy
09-03-08, 04:46 PM
Thanks for the TSB info.

This dealership is stupid.....i am going to have to show them where in the warranty manual it's specified that diagnostics are covered!!!!

Ranger
09-03-08, 10:01 PM
They are not stupid. They know what is covered and what isn't. They're hoping you don't.

ewill3rd
09-04-08, 08:20 AM
If the car is under 8/80 it should be covered, diagnosis and replacement.
If you called Cadillac Customer Care they should take care of it for you. Not sure why they are trying to pull this on you.

Ur7x
09-04-08, 01:56 PM
If the car is under 8/80 it should be covered, diagnosis and replacement.
If you called Cadillac Customer Care they should take care of it for you. Not sure why they are trying to pull this on you.

My dealer tried this with me too... This tactic is NOT uncommon... I refused to pay and threatened to complain to GM HQ... The service manager, reversed the charge.

90devilleguy
09-04-08, 07:04 PM
well that's it i'm finished with gm. The service manager would not reverse the charge for the diagnostics fee. He said because the car is not under the orginial warranty that i am responsible for the diag fees.

I am so pissed right now. I paid it anyways, so hopefully once i here back from Cadillac Customer Service they will do something about this.

Hopefully i am not screwed cause i paid for the diag fee so i could get my car back.

from the manual!!!!!

Your Rights and Obligations (For Vehicles Subject to
California Exhaust Emission Standards)
The California Air Resources Board and General Motors
are pleased to explain the emission control system
warranty on your 2002 vehicle. In California, new
motor vehicles must be designed, equipped, and built
to meet the states’ stringent anti-smog standards. GM
must warrant your vehicle’s emission control system
for the periods of time and mileage listed provided there
has been no abuse, neglect, or improper maintenance of
your vehicle. Your vehicle’s emission control system
may include parts such as the fuel injection system,
ignition system, catalytic converter, and engine
computer. Also included are hoses, belts, connectors,
and other emission related assemblies.
Where a warrantable condition exists, GM will repair
your vehicle at no cost to you including diagnosis,
parts and labor.

ewill3rd
09-04-08, 09:45 PM
PM sent, I can give you some information to review.
I hope it will do some good, the SM may just be confused or there may be something we don't know.

AJxtcman
09-05-08, 08:28 AM
PM sent, I can give you some information to review.
I hope it will do some good, the SM may just be confused or there may be something we don't know.

This is my story The Service Manager wasn't confused the Writer was!

When I took Jodie down to the Charlotte area in May I stopped in at a Chey/Caddy dealer and talk with the Service Manager for about an hour. When I came out the truck was not running:hmm:
Jodie said it started dinging and died. :eek: OK I should have asked to use a Tech II, but I didn't
The truck started and drove fine until 3 days before I left. It died out several time and it would not restart right away. :mad:
I drove down to visit a friend and borrowed a scan tool in Columbia SC about 90 miles. The truck ran perfect. The DTC stored was for an ECM internal failure :eek:
Jodie was staying with her boss and her husband, so they drove her to work and the truck sat.
She used it a few weeks later to look for an apartment and it would only run for about 20 minutes :rant2: She was calling me every time it stalled.
Jodie needed to return to Wisconsin for 2 week in June for the oldest Graduation and her Graduation party and we didn't want to try to deal with the truck in the shop.
The Monday after she got back she attempted to take it to the dealer. It didn't make it. It had to be towed.

She had to sign for the Tow, Rental car, and Diagnostic time because the truck was now 2 days out of the 3/36 warranty.
I told her to sign for it. :yawn:

I talked to the service writer and asked him to order a ECM and atleast get it coming.
He said I don't think so.
The tech determined that it had a bad battery and they replace it.
:rolleyes: yeah right. Jodie OKed the battery at our cost. :cool: Jodie told them to let the truck run after the battery was installed. We never had a Battery issue, but the 4 ways were on waiting for the tow truck
Then they called back and said the truck wouldn't run any more and needed the ECM. It was going to be $XXXX more. I told her to tell them it was under warranty! :rant2: She told the guy and he said NO. She asked to talk to the Service Manager (the one I talked to for an hour). She left a Voice Mail and he never returned the call, but the service writer did and he said that they would cover the ECM, the Tow, one day of rental and Good Will the Battery. :stirpot:

The ECM had to be Special Ordered and it would be 3 to 4 days out. We would be responsible for the first day of rental and how ever many days until they got the PCM. Jodie Said OK. of course she was calling me constantly.

The ECM showed up the next day. That is exactly when I said it would. They over nighted it.

The service writer now left a message for Jodie that she just owed for the first day of rental. :stirpot:
That is a bunch of BS. I do this for a living and that is BS.
Jodie missed the message and actually picked up the truck the following night. :hmm:
We paid for 1 day of rental at $30 for returning it a day late.


OK 8/80 emissions warranty will pay for rental cars, over night charges, Diagnostic time, the emission related parts covered, Parts needed to change that part, Hotels, and tows. Just like the bumper to bumper will cover.

If you were out of town and your ECM fails on your trip at 79K. GM will pick up the tab including the Hotel. I am not sure how you would get reimbursed for the Hotel, but I have heard that GM will do that

BTW a P0420 Labor Operation has additional time for Diagnostic :stirpot:

Some one is double dipping :shhh: That can get someone in trouble with the General :eek:

90devilleguy
09-05-08, 10:12 AM
AJ-

800-868-5664 ask for Peter the service manager, tell him all this and he will throw it right back in your face. I fought with him in person yesterday and he would not believe me even when i showed him the warranty except that i posted above!!!!

I have a idea that will really hurt this guys reputation. I'm make some phone calls.....

90devilleguy
09-11-08, 05:35 PM
OK Everyone, Here's the verdict on my claim to Cadillac Customer Service.

They still find me responable for the diag fee.

Reason why is because my car has 2 aftermarket mufflers on the back and they feel that this could be a cause for the problem. BS!!!!

If you remember I told the dealership about the Bad Ign Coil problem i had 2 months before and they said to me that it was probably due to that.

On my invoice it never says that they did the repair and replaced the cat as a means of goodwill even though i have aftermarket mufflers on the car.

I think this is WRONG, I need to take this to the BBB now to deal with it.

All for a whopping 110 bucks they have to be this f'n greedy.

/Rant

ewill3rd
09-11-08, 09:46 PM
Wow, sorry to hear they are being so stubborn.
:(

Ur7x
09-12-08, 12:23 AM
sue the ba$tards!

90devilleguy
09-17-08, 04:28 PM
So i had to speak with someone else at GM and now this person says that the dealership charged me the the Diag fee because of my aftermarket mufflers that i have on the car. They needed to verify that the cause for my PO420 code was not cause from the aftermarket mufflers. That it took longer then usual to verify and this is the reason why i get charged.

Do i have any recourse????

ewill3rd
09-18-08, 09:24 AM
Ask them why aftermarket mufflers would increase the difficulty of the diagnosis.
The cat either works or it doesn't. They are hoping you won't be smart enough to realize that. (as much as I hate to say that.... and you didn't hear it from me)
The catalyst monitor runs from two sensors, one before the cat and one after, what happens after that is meaningless.

Submariner409
09-18-08, 11:11 AM
If I'm not mistaken, some Cadillac dealerships actually install CORSA and BORLA aftermarket exhaust components.......I know that Fitzgerald Cadillac in Annapolis has a CORSA system for a CTS hanging up in the wheels-tires-chrome-wood section of the waiting service/showroom area. If the dealer itself installs the stuff, it sure doesn't sound like it voids any GM warranty. As ewill3rd opined, cat changes, yes. Catback changes, no. The reason this dealer is hassling YOU is because THEY didn't install YOUR mufflers.

Ur7x
09-18-08, 04:26 PM
Ask them why aftermarket mufflers would increase the difficulty of the diagnosis.
The cat either works or it doesn't. They are hoping you won't be smart enough to realize that. (as much as I hate to say that.... and you didn't hear it from me)
The catalyst monitor runs from two sensors, one before the cat and one after, what happens after that is meaningless.

Amen. As I understand the test for a bad cat, they remove the front O2 sensor, replace it with a presure tester and they measure the result...

I agree with you, it has NOTHING to do with a cat back system. This guy is taking one up the tail pipe.

ewill3rd
09-20-08, 10:45 AM
We install Corsa cat-back systems and have never had a problem unless the cats themselves were swapped out, and even then...

Actually a pressure tester would give you an indication that the cat is plugged, however that doesn't necessarily mean it would fail a P0420. Of course it makes sense that it would but...
A partially plugged catalyst could still function but it may cause drivability issues, and a cat that fails a P0420 test may be as free flowing as a new one.
Just to add a bit of gasoline to this fire....

On a conventional O2 sensor system here is how I run a test on a converter to see if it is bad.
I connect a scan tool, set up the display to show me the voltages for the pre-cat and post-cat sensors. I start the engine and run it until it achieves closed loop. The Tech 2 scan tool allows me to do a "live plot". Basically that means I can see a graphical representation of the display data rather than staring at numbers. Once in closed loop the pre-cat sensor value should be switching rich-lean-rich-lean and the post-cat sensor should be stable.
That lets me know that the catalyst is processing the gases to maintain the emissions on the vehicle.
If the post-cat sensor switches rich-lean-rich-lean on the display lagging the front center by the time it takes the gases to travel through the cat or from sensor to sensor I know the cat is bad.

The diagnostic chart might take you down a longer path but that is what it boils down to. As you can imagine that process would take about 15 minutes. GM warranty pays 18 minutes for diagnosis and frankly these days with as many as I have seen the diagnosis for a P0420 boils down to it's mere existence. If the code is set, the cat is bad.
There are so few factors (as I have stated before) that could actually cause a P0420 to set multiple times that it is amazing to me to think that an experienced tech would require more than reading the code and ordering the part.

That being said, I hate to keep fueling this fire but I think it is terribly unprofessional that you are getting such a runaround over something that is so ignorant. No matter how much "ammunition" you have I don't think this dealer is going to budge, but I'd take this as a $100 lesson to not go back there. You might also caution the people you know.
I hate to see a dealership digging themselves into a hole like that, particularly with the automotive market the way it is right now. I am all for them looking out for their tech and their bottom line but it is pretty dumb to do that at the expense of pissing off your customers and making them not want to ever come back.

I have no issues doing a favor here and there for my customers (which can frustrate my boss sometimes :D) to keep them happy because if they don't come back later, I don't get paid and I am out of a job.

ewill3rd
09-20-08, 10:49 AM
Oh I forgot, to be fair, it seemed that your dealership did do some checking to be sure there were no external causes for the catalyst failure but in my experience the cause of the failure is usually chemical in nature, and long gone by the time the code actually fails. I'd almost let it go if they actually said they did all the testing to be sure the new cat would not go bad, but again they would have to tell you BEFORE the work was done that the charge would be there.

90devilleguy
09-21-08, 10:25 PM
Oh I forgot, to be fair, it seemed that your dealership did do some checking to be sure there were no external causes for the catalyst failure but in my experience the cause of the failure is usually chemical in nature, and long gone by the time the code actually fails. I'd almost let it go if they actually said they did all the testing to be sure the new cat would not go bad, but again they would have to tell you BEFORE the work was done that the charge would be there.

If anything i'm just pissed because 3 people have told me 3 different reasons why there is a charge for the diag. I was told after they did the initial diag work that the cat would be covered under the emissions warranty but they were going to charge me the diag fee and i told them no way to the diag fee, why should i? And they never gave me a straight answer. They just said that they have to charge that, I looked right in the warranty book when on the phone and said what it was written about the diag fee being waived, the guy at the dealership was like well you can talk to the service manager then. The only final thing i said to the service manager is that i need my car back asap and to order the cat and i'll deal with GM then and let them know that you are screwing the customers. the SM didn't like that and said well if my field manager came in and saw that there were aftermarket mufflers on the car he would say no way to the warranty work...the SM then adds he's doing this out of goodwill......BS



/rant

Angus Young
10-15-08, 08:38 PM
I have this code and its brother code P0430, dealer advised me today both cat's are bad, they tested and cleared the codez, I cleared the codes myself but they just wont go away, dealer wants 2 grand to replace them, I was wondering if headers are available for the 05 STS V8, if so then does anyone know how the O2 sensors fit on the headers? If headers are not an option, then where would be a good place to get a new pair? Rock doesnt carry them, and as I understand the cat's are a part of the exhaust manifold so the whole thing must be replaced. My warrenty for the emmissions has expired. Any alternative solutions??
Thanxx

Submariner409
10-15-08, 09:28 PM
Angus, This is in the wrong Forum: You need to go up to the 2005+ STS threads up ^^^ there.

(When you get situated, click on your username and update your profile and personal info so that your car, model, year is reflected in your heading, like mine ^^^.)

koolfred2002
07-08-10, 11:45 PM
I have a 2002 cadillac deville throwing the P0420 code! I checked all o2 sensors, fuel pressure and fuel filter everything checks ok. I resealed the intake and replaced the plenum a year befor the cat went bad. no vaccum leaks. Does any one know of a aftermartket cat and to correct part # that will work. I sorry i beleave in oem parts but I refuse to spend over $1000 on this part. I alredy tried the eastern catlytic cat It did not work, I was able to get a refund. I heared that walker and catco make good cats that will work but i need part #s. any help would be apretiated. Thanks!

derone
07-09-10, 11:26 AM
Hey, been there, done that. I even bought one of those 'direct-fit' cats and can tell you direct-fit don't mean sh$t. Then I found that all cats aren't the same as some would lead you to believe. I had the 420 error and I have been using the Magnaflow 46006 cat for over 40k miles with no codes. It has the 2.5" in and out connections....the 46009 has 3". Double check to see which pipe yours has, as their application chart isn't that accurate. See link for more info: http://www.car-sound.com/02product/universalCARB/460.asp

Necrosan
07-09-10, 01:35 PM
You can always cheat and install spark plug anti-foulers in line with the O2 sensors to pull the O2 sensor slightly out of the exhaust stream.
Has worked on EVERY OBDII car I've tried it on with P0420 code.
You can cut the catalytic converter out safely at that point.
If you're in a state that does inspections though, be prepared to explain yourself next time they put a mirror under your car.
Here's a link to a comprehensive post explaining this process better: http://www.solaraguy.com/viewtopic.php?f=20&t=43374
Good luck! Saved me a couple hundred bux on a few cars I could give a rats ass less about emissions on, seeing as the anti-foulers are only about $3 for 2 of em.

koolfred2002
07-09-10, 05:45 PM
Thanks! did you install it your self or did you have an exaust shop do it? looks like there is some fabrication involved! can I cut exaust flange of the old cat and have it welded to the new one! also how is the performance of the car. mines is a bit slugish at times because of the partilly clauged cat.

derone
07-09-10, 06:53 PM
The shop measured the length of the 46006 and then cut the corresponding length of exhaust pipe including the old cat out with a chain pipe cutter. He welded the new cat up in the empty space. Only charged $35, but it was a rural area shop. The car runs like a top, haven't had any engine/tranny issues, other than an idler pulley and leaky coolant reserve tank and leaky oil pan. Those were fixed long ago. I just replaced the rear shock mounts since the shocks were sitting way up in them...next week are the strut mounts in the front. 114k miles strong and soon firmer w/o that bobbling noise over certain bumps.

koolfred2002
09-15-10, 11:36 PM
thanks man! I ordered up a magnaflow 46009 with the 3 inch inlet outlet only $189 free shipping from auto parts wharehouse. the installer cut the OE converter from the flange adaptor,welded the magnaflow up and welded a 3.0 to 2.5 reducer from pep boys to the end of the cat and insalled it in the car. car runs like a champ p0420 code gone no ck engine lamp. car has been fixed 2 monthes now. im very happy that i did not have to shell out over $1000 to fix this. next project replace front motor and rear trans mounts, not completly shot yet but starting to go bad.

Doug99
09-17-10, 12:29 PM
I had this installed on my 99 Deville last week , car runs great no codes after 300 miles -

MagnaFlow 94009 Universal Catalytic Converter
http://www.amazon.com/gp/product/B000COTIKM/ref=oss_product

mtflight
10-15-10, 01:08 AM
Any reduction in performance from using the magnaflow? I am floored by the prices I've seen on the OE. Even the Walker (which is OE exhaust provider, Idk about the CAT though) is over $330.


No codes yet, but it started to smell like rotting eggs a few days ago :(

How much time do I have, before the code pops up?

Ranger
10-15-10, 01:07 PM
Any reduction in performance from using the magnaflow? I am floored by the prices I've seen on the OE. Even the Walker (which is OE exhaust provider, Idk about the CAT though) is over $330.


No codes yet, but it started to smell like rotting eggs a few days ago :(

How much time do I have, before the code pops up?

I seem to recall our old Guru mention that that was a sign of a rich mixture. Might want to check the FPR.

mtflight
10-15-10, 02:45 PM
I seem to recall our old Guru mention that that was a sign of a rich mixture. Might want to check the FPR.

Thanks Ranger. I keep crossing my fingers that it's something like that or bad gas. Recently I've dealt with rear shocks, now my ac mode actuator, AC and the egg stink. I don't have any FPR symptoms (had more on the Eldo but the FPR was fine on that one), but this is so simple, I'll check it out.

EDIT: Checked the FPR and found no leaks. Sulphur smell is not so prominent, but rather weak, possibly diminishing. It could be a bad batch of gasoline (although I only get Top Tier)?

Any other suggestions? no codes.

Ranger
10-15-10, 05:31 PM
Try a different brand of gas and see what happens.

koolfred2002
10-17-10, 06:11 PM
Any reduction in performance from using the magnaflow? I am floored by the prices I've seen on the OE. Even the Walker (which is OE exhaust provider, Idk about the CAT though) is over $330.


No codes yet, but it started to smell like rotting eggs a few days ago :(

How much time do I have, before the code pops up?

No reduction in performance! car runs like a champ! its the only cat that I know off that will pass. No tellin how long they take to set. the computer will set the code as soon as the after cat o2 sensor reads out of range indicating that the cat is no longer efficient.

koolfred2002
10-17-10, 06:14 PM
I would wait till it sets a code! or If the car runs poorly to replace it.

mtflight
10-17-10, 10:18 PM
I would wait till it sets a code! or If the car runs poorly to replace it.

Yeah, I'm going to wait. Seems like my battery is probably going to go in a couple of months first. My yearly inspection is due by the end of this month, so hopefully no codes will be set until after I pass emissions.

Probably too much to ask, but did you say your exhaust tone changed, or become a little more aggressive? That's what excites me lol. A video or audio clip would be great if at all possible.

koolfred2002
10-19-10, 10:29 PM
yeah it did at first thats because i had a small exaust leak at the rear were i clamped it in place.I took it to an exaust shop and had it welded. now its nice and quiet it was not real lound but had a nice performance tone. I tell u what! I cranked it up with the cat off while replacing it and it sounds like a mussle car with a performance cam and headers. But to answer ur ? is close to stock when installed correctly. If u want a nice performance sound u may wan't to look at changing the 2 rear mufflers.ck out videos on youtube type cadillac dts exaust,or cadillac corsa exaust to get an idea of the sounds.

koolfred2002
10-19-10, 10:33 PM
hopefully this link will work.
http://www.youtube.com/watch?v=d0147WU0e90.

koolfred2002
10-19-10, 10:37 PM
U didn't think a caddy would sound like that did ya. I would not mind having that exaust but over $1000 freakin dollars and I think it my be to loud! but I would Love to have those exaust tips.

Ranger
10-19-10, 10:49 PM
You don't have exhaust tips like that? You could probably find a set on Ebay.

Submariner409
10-20-10, 10:54 AM
U didn't think a caddy would sound like that did ya. I would not mind having that exaust but over $1000 freakin dollars and I think it my be to loud! but I would Love to have those exaust tips.

Take it from someone who has had the CORSA system on his STS since 11/06: It's NOT loud unless you want it to be - absolutely silent at cruise but stick your foot in it and it will wake the dead. The problem with these factory exhaust systems is not the cat or mufflers - it's the small pipe from the cat to the Y, the Y itself, and the pipes to each muffler. CORSA addresses all that and more. If you want the real thing, be ready to pay for it. Mufflers alone may sound good but they don't do squat for performance (more noise is more power, right ?).

CORSA sells tips, mufflers, parts at www.corsaperformance.com

Systems for 1999 and + at www.AutoPartsWarehouse.com

screech858
01-04-12, 02:29 PM
Hey, been there, done that. I even bought one of those 'direct-fit' cats and can tell you direct-fit don't mean sh$t. Then I found that all cats aren't the same as some would lead you to believe. I had the 420 error and I have been using the Magnaflow 46006 cat for over 40k miles with no codes. It has the 2.5" in and out connections....the 46009 has 3". Double check to see which pipe yours has, as their application chart isn't that accurate. See link for more info: http://www.car-sound.com/02product/universalCARB/460.asp

Did you notice and difference in sound when swapping out the factory cat and installing the magnaflow one?

Submariner409
01-04-12, 04:46 PM
derone hasn't been here for over a year. With a stock exhaust system there will be little, if any, sound change when replacing a converter. The original converter is a honeycomb ceramic high-flow unit - it's the resonator that smooths out the front exhaust pipe sound pulses.

screech858
01-04-12, 11:57 PM
cool thanks man

NHRATA01
01-17-12, 02:09 PM
derone hasn't been here for over a year. With a stock exhaust system there will be little, if any, sound change when replacing a converter. The original converter is a honeycomb ceramic high-flow unit - it's the resonator that smooths out the front exhaust pipe sound pulses.
I might have to disagree with ya on that one sub. In my experience the factory-style honeycomb ceramic units tend to absorb much more of the exhaust volume then a straight-through metal matrix design of a typical aftermarket cat.

For many years I had essentially a straight-pipe exhaust with a resonator on my LS1 Trans Am (SLP loudmouth). It sounded nice with the factory converters. It was still liveable with an old header manufacturer that utilized honeycomb ceramic cats on the headers. When I switched to a set of American Racing headers with the metallic style cats, basically the magnaflow ones, it became unbearable. And I tend to have a pretty large tolerance to exhaust noise!

MoistCabbage
01-20-12, 08:46 PM
Straight pipe with resonators, no mufflers---not a stock exhaust system.

Swapping cats may make some slight difference, but nothing too noticeable (with mufflers).

dtaylor
02-28-12, 10:43 PM
I also have the p0420 code. I'm gonna look into the magnaflow 46006 I hope this will take care of this code Dont care about sound I just want this engine light GONE

oldmanlesabre
04-21-12, 02:22 PM
so apparently the 'new' magnaflow seems to work, but the model before the one out now is complete garbage? so many mixed reviews. what is difference with 46006 and 46009? just got done reading this thread:
http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/176108-2001-deville-clean-throttle-body-p0420-4.html

and others...

mustangrr
08-28-12, 05:35 AM
PO420 has got me too...
My 2003 SLS with 77K miles just popped the SES and analysis showed a PO420 code. Local mechanic told me the catalytic convertor was bad. I had him replace it to the tune of $550. About a week later I started noticing my engine was running oddly (the SES light had gone off a couple of days earlier, after having had the CAT replaced) - rough and weak at stops, but powerful when accelerating, almost like it had a modified cam in it suddenly. I started thinking about timing, and rich & lean fuel mixtures - but once under the hood I discovered a loud sucking noise, and realized I had a vacuum leak. I took the car to my local Chevy/Cadi dealership, where they analyzed the problem and came up with a cracked Throttle Body Boot. After 3.5 hours of labor, a new Throttle Body Boot, $400 and a reset computer registry, I was on my way. Suddenly, two weeks later, my SES has come on again. Took the car to a local Autozone and had them do the computer analysis and the code came up PO420 again!!??

Having read all the previous posts in this thread, I'm wondering if the replaced CAT was an inferior after-market, and perhaps has failed, or not able to meet the standards anymore - or, could the sudden cracking of the Throttle Body Boot (TBB) and the resulting vacuum leak cause the CAT to fail? Is this logical thinking on my part? I ask because I'm not sure where to start looking for a remedy. My first thought is to find out if the replacement CAT was worthy of Cadillac usage. Any other thoughts, suggestions and/or remedies will be appreciated.

PS. Because the SES light went off between the CAT replacement and the onset of the vacuum leak due to the cracked TBB, I assuming this new PO420 code is a current reading and not a history reading, though I'm not positive right now. I have been driving the car with the SES light on for about 4 days now without any notice of problems.

Submariner409
08-28-12, 10:31 AM
GM refers to your "throttlebody boot" as a "plenum". P/N 12555840, about $30.

Your car has its own built-in code memory/reader/scanner system right in the DIC. Study the sticky post ^^^ "How to pull codes". You want the proper procedure for the cars with 3 DIC control buttons on the right and OBD-II (obd2) protocol. Practice, write down all codes and whether each is Current or History, then return to the sticky to open the link with "obd2" in the address to get to a Master Index of all P,B,C, and U code definitions. Always post definitions along with codes.

mustangrr
08-28-12, 09:57 PM
Thank you Submariner409 - Sounds like a mouthful of terminology I have to research and catch up on. I assume my logic about researching the replacement CAT is okay, once I determine whether I'm looking at historical or current coding, right?

mustangrr
08-28-12, 10:04 PM
And you're right on the Plenum cost - the dealer charged me $36.60 for it, and $330 for labor...

Submariner409
08-29-12, 11:53 AM
Yeah, the labor is what gets you - the intake manifold R&R is 2.5 hours, the throttlebody is another 1 hour.

A good wrencher can do the whole thing in the driveway in 2 hours.

mustangrr
08-29-12, 04:09 PM
That R&R you mention, does that include removing & replacing the intake manifold gasket? I ask because this same dealership told me last October that I had a leaking I/M-Gasket, and charged me for replacing it. When I returned to them 3 weeks ago with another vacuum leak, I told them I suspected the I/M-gasket they replaced last year might be the source of the current vacuum leak. They said they'd check and came back with the Throttle Body Boot story. Now I can't help but wonder if they "stiffed" me. I hate not being able to check their actual work afterwards... I can see that "knowing your mechanic and having trust" can help alleviate a lot of suspicion and distrust.

If I may, I have another question for you Submariner409: Is it possible that the vacuum leak from the Throttle Body Boot damaged the "new, replacement" catalytic convertor that was installed 3 weeks earlier?

Submariner409
08-30-12, 03:31 PM
There is no intake manifold gasket in our 2000+ engines. Each port uses an individual silicone seal ring - a formed "O-ring" if you will - and they're 99% reusable. A GM dealership charges about $17 apiece for them during replacement - the entire set of 8 can be bought at a NAPA or online for $14. RockAuto is currently selling the Dorman plenum AND intake seals for $15.45 plus shipping. (Engine: intake coupling, Dorman 911010 [GM # 12555840])

An intake side vacuum leak causes lean fuel mixtures - rich fuel mixtures are the cause of cat overheating and damage.

mustangrr
08-31-12, 03:50 AM
Thanks again for the first hand information and great illustration. I don't know much of anything about this Northstar engine, and certainly don't have any design on performing my own work. But I do like learning the mechanics and workings of the machine, and how my driving wears on it. You appear to have a wealth of knowledge and experience and I respect that of you, especially when you are so enthusiastic and cordial about sharing it. I thank you for this exchange of information.

I took my 2003 SLS (78K miles) into another Chevy/Cadillac dealer yesterday morning and told them my SES light had been on since 8/20 and explained the history of the Cat and Plenum having been replaced recently. We confirmed the DTC was PO420, again. They took the car in for more detailed analysis. [They quoted me a standard $115 fee for the full analysis, here in Mass., which is about $30 more than the dealer in my hometown in NC charges - just an observation] They contacted me a few hours later and told me that the forward O2 sensor appears to have been repositioned during the recent repair job, and that is was located directly under the air conditioning condensation drain/or runoff. This caused O2 damage ($225 replacement) and rusting of the wire leads and 'coupling/bracket' ($150 replacement). They stated they had to order the parts from Philly o/n and that they'd have my car fixed tomorrow.

Of course, I'm not thrilled that I have to spend more hard-earned money, so soon, but I am thankful I didn't have to replace the catalytic converter or plenum again!

Is there a reference or link you can refer me to where I can look at detailed diagrams of the '03 Cadi engine compartment and know what I'm looking at? Maybe even a schematic of the Northstar engine broken down? I do enjoy reading reference materials and doing my own research from time to time.

Thanks again for your info Submariner409.

Submariner409
08-31-12, 11:37 AM
For fingertip reading including the GM service manual, labor times, recalls, Technical Service Bulletins (TSB), Regular Production Options (RPO), diagnostic trees and illustrations, try a subscription to www.alldatadiy.com . You can directly print pages, diagnostics, parts illustrations, specification tables right from the site. There is so much info in each individual car model (Alldata is NOT generic) that you have to get used to drilling down to what you want.

Ranger
08-31-12, 03:44 PM
Is there a reference or link you can refer me to where I can look at detailed diagrams of the '03 Cadi engine compartment and know what I'm looking at? Maybe even a schematic of the Northstar engine broken down? I do enjoy reading reference materials and doing my own research from time to time.


Try here. When you get to the page you want, click on the blue "More Info" button for a diagram.
http://www.gmpartsgiant.com/cadillac-parts.html

Here's another.
http://parts.nalleygmc.com/default.aspx