: 2002 sts engine codes



kkucher
02-24-08, 12:02 PM
I have a 2002 STS, took it to Autozone and had them hook it to a computer. The car is sputtering, stalling, hard to get going and won't go very fast.

These codes revealed themselves when hooked to the computer. P0101, P0404, P0420.

Any ideas what these may becaused By? can I fix this myself? How much should it cost if I take to a dealership? I live in Metro Detroit area of Michigan. Thanks for anybdies help and this is a great site.

FrankT
02-24-08, 02:11 PM
P0101 Mass Air Flow Sensor Performance
P0404 Exhaust Gas Recirculation (EGR) Open Position Performance
P0420 Catalyst Catalyst System Low Efficiencey

Fix the Mass Air Flow problem and EGR valve problem before proceeding with the P0420.

CadillacSTS42005
02-24-08, 03:11 PM
you need
A MAF
A EGR Valve
and a CAT

a EGR and driving it while running like that failed the CAT, you melted it and clogged it

your looking at at least 2 grand if you go for OEM parts

FrankT
02-24-08, 05:41 PM
you need
A MAF
A EGR Valve
and a CAT

a EGR and driving it while running like that failed the CAT, you melted it and clogged it

your looking at at least 2 grand if you go for OEM parts

Woowa, slow down Jason.
I would start by diagnosing the EGR first. An EGR valve that is sticking open will change the airflow and may cause a loss of vacuum that may also set the P0101 code or a lean code.

You are correct about the damage that may have been caused to cat, a misfire is the worse thing to put a cat through, they hate it, I have heard some case where a misfire killed a cat in less than a minute. But, if not melted or broken up they can restore itself somewhat, though the life of the cat has been shorten.

A restricted air intake duct

A collapsed air intake duct
A misaligned air intake duct
A dirty air filter element
A deteriorating air filter element
Any objects blocking the air inlet screen of the MAF sensor
Any debris or contamination on the sensing elements of the MAF sensor
Any vacuum leak downstream of the MAF sensor
A poor vacuum connection at the MAP sensor
Any water intrusion in the induction system
A restricted exhaust system

All of the above can set a P0101 too. One thing at a time, diagnose and check circuits before replacing an expensive part. You also might want to try and clear all codes and see what comes back.

Submariner409
02-24-08, 07:08 PM
The OP needs to learn to pull and read his own codes. You don't need to go anywhere: the car will do it for you. The instructions for your '02 are at the top sticky threads in N* performance and Tech tips.

Ranger
02-24-08, 07:48 PM
:yeah: and :welcome:
I'd start by cleaning the EGR valve. Instruction are in the Tech Tips section.

CadillacSTS42005
02-24-08, 08:24 PM
hey im just basing it on the codes lol
ESI confirms my diagnosis

if the car wont run and has a SEVERE loss in power along with driveability issues and is throwing a CAT code along with an EGR code, my exhaust knowledge tends to say he melted the cat and it aint a cheap one on these cars lol

kkucher
02-25-08, 02:23 PM
I have been given a quote for the, P0101, $295.00 with tax any idea if the car will run if this is replaced? It sounds like to me that it's a wait and see if I damged my CAT or not. Should I suggest that the Cad. service techs should clear the codes first or will the look at me strange of I suggest that. Thanks again for all the helpful suggestions.

Mark

FrankT
02-25-08, 09:27 PM
Mark,
Do to the fact that the car lacks power I would drop the exhaust just before the cat and see it the problem goes away, it's quick and easy. I don't think you have a bad MAF, If you had a bad MAF then after the P0101 set the PCM would will go to a default known good value and the car would run OK. A restricted exhaust system will set P0101, drop exhaust system and go from there.

Like Jason said,
if the car wont run and has a SEVERE loss in power along with driveability issues and is throwing a CAT code along with an EGR code, my exhaust knowledge tends to say he melted the cat

I agree with that statment 100%

kkucher
02-26-08, 03:39 PM
I took it the dealership, the service guy was very cool. He is replaceing the CAT under the warranty, there is something for GM to replace within warranty under 80k miles.

They are going try to reset codes and go from there, they seemed very cool.

Thanks for all the input guys.

FrankT
02-26-08, 06:58 PM
He is replaceing the CAT under the warranty, there is something for GM to replace within warranty under 80k miles.
Thanks for all the input guys.

Now you are on the right track. I bet the Cat takes care of all three codes, and you are welcome.

Crown Vic Owner
02-26-08, 08:46 PM
good thing on the cat.


Honestly, the EGR CAN NOT clog a cat AFAIK.

Submariner409
02-26-08, 09:02 PM
Crown Vic, A stuck/slow EGR valve causes a lean signal, among other things, from the downstream O2 sensors, driving the engine rich, which overheats the cat.

Crown Vic Owner
02-26-08, 09:08 PM
Crown Vic, A stuck/slow EGR valve causes a lean signal, among other things, from the downstream O2 sensors, driving the engine rich, which overheats the cat.

A bad EGR valve in these cars make the engine run RICH?


Interesting. Most cars default to a default AFR that is not rich OR lean, just normal.

this happens anytime the CEL is on i assume?


So what happens if the CEL is on for something else, say, idk, TCC clutch?

kkucher
02-27-08, 09:48 AM
Now you are on the right track. I bet the Cat takes care of all three codes, and you are welcome.

FrankT I see your from Michigan, where abouts? I live in Shelby Twp.

FrankT
02-27-08, 11:49 AM
kkucher,
Wow, Shelby Twp, :cool2: You are East of me.
I'm from the Livonia/Northville area. Maybe we'll run into each other some time and have :cheers: one. Good luck on your car, let us know how it turns out.
Take Care,
Frank

FrankT
02-27-08, 12:22 PM
Crown Vic, A stuck/slow EGR valve causes a lean signal, among other things, from the downstream O2 sensors, driving the engine rich, which overheats the cat.

Good answer Sub!:thumbsup:



A bad EGR valve in these cars make the engine run RICH?


Interesting. Most cars default to a default AFR that is not rich OR lean, just normal.

So what happens if the CEL is on for something else, say, idk, TCC clutch?


this happens anytime the CEL is on i assume? Yes, the PCM/ECM can substitute a known good value or a default value once the MIL sets. The car will tend to run ok, but, it will not meet emissions, it also helps prevent a walk home, that would not make you very :bouncy:.
There are different default actions the ECM/PCM can take depending on what code sets. For Ex. to name a few remeidal actions or defaut modes,

Fuel Limiting
Forced Idle
Forced Engine Shut down
Acceleration limiting
Throttle default mode
Limited throttle mode
Fuel Cut-OFF
Defaulted sensor values depending on what sensor fails.For a TCC fault like you are asking about it can
inhibits 4th gear if the transmission is in hot mode.
I probably missed a few modes, but you should get the picture.

Submariner409
02-27-08, 12:53 PM
Crown Vic, If you wade through the Helm FSM for just about any N* engine/car, you'll find that the diagnostic paths for darn near anything electronic connected to the engine are frustrating, convoluted, and just plain gibberish. I'll bet that even eWill3 and AJ tear their hair out trying to diagnose faults.

One problem is that.......one problem may create others! Not intentionally, but as part of the original fault. When I said that a slow or stuck EGR valve could overheat a cat, that's only one of a dozen consequences of the same fault. Another offshoot of a bad EGR system is a persistent, low level part-throttle ignition ping or knock. Very prevalent in an EGR setup run by carburetor/manifold vacuum signals.

Anyhoo, one code or fault generally isn't the whole enchilada.......