Cadillac Owners Forum banner

Sporadic SES light and exotic codes - friend's 2004 DTS

27K views 184 replies 10 participants last post by  Ranger 
#1 · (Edited)
Here I was thinking my Cadillac troubles are over but ... A friend owns a '04 Deville DTS and was complaining to me about the SES light coming on and off randomly. He asked me to have a look since I went through so much trouble with my old Seville. During a test drive I didn't notice anything strange but a rough idle with slightly elevated rpm that totally goes away the warmer the engine got. The Deville also has abyssal gas mileage of below 13 MPG. After a couple of miles the SES light indeed came on and stayed on until we parked the car. 10 minutes later we got back in the car and drove the same route back with the light not coming on at any point in time.

Strangely, it is not throwing any code that can be read out with the internal code reader but two codes concerning the front seat adjustment motor. One remains of my old Seville was an external code reader that threw out the following:

Trouble Code: P0174
ABSLT TPS(%): 14.5
ENG SPEED(RPM): 2027
CALC LOAD(%): 50.2
MAF(gr/S): 29.45
MAP(KPa): 71.0
COOLANT(°C): 94
IAT(°C): 27
IGN ADV(°): 39.0
SECOND AIR: ATMOS
ST FTRM1(%): 8.6
ST FTRM2(%): 0.0
LT FTRM1(%): 21.1
LT FTRM2(%): 24.2
VEH SPEED(KPH): 78
FUEL SYS 1: CLSD
FUEL SYS 2: CLSD

After some quick research through this board, it could be a vacuum issue. We did a quick check of all apparent vacuum lines and the only one showing clear signs of degradation is the one circled yellow in the picture below. The rubber hose part is cracked by an inch (on the bottom) and the hole connection is very shaky and loose.

Auto part Fuel line Automotive fuel system Engine Vehicle


Unfortunately, I have no idea what that particular part is or what it's supposed to do - and therefore does not know whether this could be a/the cause for the SES light. I also read here on the boards that I should just get a can with some carb cleaner or so, carefully spray the vacuum lines, and listen for rpm changes to isolate any vacuum leaks. I'd like t do that but was unable to find a picture or diagram clearly marking all candidate spots. Is such a treasure hidden deeply somewhere?

EDIT: I didn't notice this at first with the code reader: P0174 is marked as "pending" while P0171 was "confirmed". Don't know how that translates into the H/C marks with the in-dash reader.
 
See less See more
1
#132 ·
The intake is subject to a LOT of PCV flow, and that "dirty air" is loaded with oil vapor and other nasties boiled out of the (normal) engine oil. Don't sweat it - you can see that the valves and lower port are washed clean by the fuel injector spray pattern. You could go crazy and attempt to hot tank the manifold and clean out the ports, but it would all be back in 5,000 miles. Normal. The trick is to do a once-a-year dedicated throttlebody cleaning, vacuum line check, and let it go at that. How-to's in the Cadillac Tech Tips.

The vacuum hose leak - that's the PCV dirty air lne - and that is subjected to 100% manifold vacuum. A leak there is almost as bad as a plenum crack. Spare parts on the Help! racks at large parts stores.
 
#134 ·
Guys you're life savers. I saw the inside of my Audi diesel engine once and it was nowhere near that gunky. I immediately assumed the worst ...

Anyway, in addition to the broken elbow, the two first screws on the intake manifold felt awfully loose. The plenum turned out to be in really good shape but since we already had a brand new one and the old gaskets looked fairly flat, we put it in. No codes or issues so far.

Although it might be too early to celebrate, I didn't notice any gurgling after the new reservoir cap was in place. I have my fingers crossed on that one, too. Thanks for all your help!
 
#136 · (Edited)
Hi Mike - it started out with a set of sporadic, totally intermittent codes fired by a 2004 Deville. In between with the help of the fantastic people here, I was finally able to address many of them. The issues buried within the nine pages read like a list of typical weaknesses of the N* engine and the Deville. Since starting this thread, I: repaired several vacuum leaks in the hoses, cleaned the TB, changed the oil pressure sending switch, identified an tampered cooling system "fix", unblocked the hollow bolt and coolant urge line, replaced one totally missing PCV line, cleaned a surge tank floater sensor, replaced the plenum, cleaned and replaced the gasket for the MAP sensor, corrected a non-sealing air filter, bled air out the brake system, convinced an actuator to work, replaced a missing clamp at the brake booster vacuum line that caused a leak when braking hard, etc.

Diagnosis for me as an amateur was next to impossible due to the fluctuating nature of the faults: P171&174 only occurred when travelling > 70, the fluctuating coolant temp only when it was raining hard (not usual in central TX), the A/C actuator issue was totally random, the gurgling of the radiator cap only happened when the engine was still hot from another drive, we had powertrain codes shooting at us when braking too hard. In between, the Damocles sword of a head gasket issue came up frequently.

The reservoir cap seemed to have fixes one issue, the plenum on the other hand turned out not being in need of replacement. I also tried to shoot many pictures in between because I can tell it is very hard for newcomers to grasp what is said here. I hope it helps people like the one who found his coolant reservoir tank sensor disconnected to identify the correct cables from the wiring harness.
 
#137 ·
Update: Apparently the Deville was "burping" one massive time today. About an inch of coolant went somewhere, I couldn't tell where but at the time I had a look at it, it does not seem to have leaked.

Furthermore, P0171 & P0174 are back when the car goes faster than 80 mph. New plenum and new manifold gaskets were installed last weekend.

To make things worse, the back A/C is blowing hot air since today. Consequently, I seem to have inherited something occupying one of my parking spots.
 
#139 ·
Ranger, thank you for your willingness to always help ppl like me. I had the manifold & TB off just a couple of days ago and inspected it for damages. I replaced all gaskets and a damaged rubber elbow, cleaned the joints, replaced the plenum, inspected the hose portion after the MAF, and removed&inspected every single vacuum lines. All appears fine.

Could it be something like a weak fuel pump? I am out of ideas on what components to check.
 
#140 ·
No. Those codes are a vacuum leak, not fuel pressure related. Get a can of Brakleen, TB cleaner or such and start spraying around the manifold base, every vacuum line fitting, TB and over pressure relief valve. When you hear the RPM increase, you found your leak.
 
#142 · (Edited)
Look at my albums. The intake manifold changed in 2000 - the manifold overpressure valve is the spring loaded mushroom poppet just under the intake manifold opening to the throttlebody.

Community tab, Albums, the red Seville - 6 pages of parts and diagrams for the 2000 - 2004 engines.

I would suspect either an air leak in the PCV dirty air line or in the intake ducting at or after the MAF. I think the 2004 still had a fixed orifice - not a PCV rattle valve - so that would not be a problem.

EDIT: The intake manifold picture in question is in Album 2 page 2.
 
#144 ·
Guys, I don't know what to do anymore. I have literally covered the manifold, tb, plenum, and vacuum lines in tb cleaner but there is nothing. I inspected every millimeter of the intake duct after the MAF for aleak, none. No engine reaction at all. I thought I might just be too deaf to hear it so I set my bluetooth OBD on the job but apart from a random +/- 20 rpm there is nothing. Can anyone tell me what I'm doing wrong?

What I did see though is a slight but persistent oily dampness at the metal parts just under the coil packs. I'd assume that is bad?

And on a side note: how easy is it to remove the driver seat? It is stuck in between my friends setting and mine, making it very uncomfy to drive for either one of us. Seat motor seems to be dead, all other seat functions work though.
 
#146 ·
Update on cooling system (and more questions of course): After putting in the new cap, around an inch of coolant was lost per week. My hope accounting that to air being purged did not hold. My friend and me went over the engine with flash lights to spot coolant leaks but to no avail. To be absolutely sure, I borrowed a radiator pressure test kit and set it up. The Deville is loosing around 1 PSI per 10 minutes. When chasing down the leak point, I came up with two suspects: the hollow bolt and the purge line connector to the surge tank.

The latter was pretty obvious because I saw coolant leaking down the tank:
Auto part Bumper Automotive exterior Vehicle Helmet


The hollow bolt connector was the highest accessible point that was wet, with coolant pooling on a piece of metal under it. The other hoses down there were bone dry.
Auto part


What is a simple and easy way of confirmation? Can I simply wrap a tissue around the two spot in question, drive around, and check for wetness? Or am I creating a fire hazard here? And is this a common spot or known for misdiagnose? I'd appreciate your comments.
 
#147 ·
A cracked nipple at the purge line connector on the surge tank is common in older cars. Amazon automotive, search, $55 or so, shipped, with coolant level sensor. No, JB Weld will not.

Ethylene glycol will not burn ..........

That engine has had other cooling system work done on it - the hose clamps are not GM original, the purge line spring clamp is.
 
#148 ·
Thank you Sub. Yes, a leak in the coolant crossover and gaskets was fixed earlier his year. I found the part for around $60. Any advice on the hollow bolt while I'm in there anyway?

The comment about burning was just silly, I account that to being in the Texan sun for too long: I got the pressure tester to not have to deal with hot engine/coolant while testing ...
 
#149 ·
The coolant leak is fixed. Now I am just stuck with the P0171 & P0174 code: could anyone provide a suggestion on how to check the over-pressure relief valve? Does it definitely mean I have to take the intake manifold off again or can it be done without that? Thanks :)
 
#150 ·
P0171 & P0174 almost always point to the plenum duct. I seriously doubt it is the over pressure relief valve. The way to check it would be to listen with a stethoscope. If it's leaking, it a vacuum leak. Should be able to hear it with the naked ear, but a stethoscope will make it sound like a hurricane. The other thing might be the PCV dirty air line.
 
#151 ·
Ranger, thanks for still answering :) The lean condition only occurs when going faster than 70.

It is not the plenum. I swapped out a perfectly intact plenum for a totally new one. Both were checked for leaks. I borrowed the duct between air box and TB, it's not that. I changed the gasket of the MAP, not that either. I changed the elbow of the rear PCV? hose, and soapy-water tested all vacuum lines.

Only thing I have not changed is the gasket between the TB and the plenum metal plate but it looked intact. One observation was a sound like a HUGE vacuum leak if my friend is rapidly bringing up the RPM's: for a split second at the TB opening, a pretty loud hiss is audible. I figured that is alright since we are indeed purposely introducing lots of "new" air at this point in time.

I'll get a stethoscope and recheck - do I understand correctly that I am listening for "wind" noises?
 
#152 ·
A vacuum leak will be most noticeable at idle, when the vacuum is at it's highest. It drops as you open the throttle plate.

Yes, a vacuum leak through a stethoscope will sound like wind. Just close your lips and suck in some air with the stethoscope to your lips. it'll sound just like that, or pull the vacuum line off the FPR and have a listen for reference.

The lean condition only occurs when going faster than 70.
That's odd. Maybe not vacuum related.
 
#153 ·
Still no luck. Only thing that was sounding like a vacuum related issue is a slow pressure relief (like slowly getting the air out of an air mattress) when I switch the car off on the right side of the intake manifold by the power steering pump. However, the center line, elbows, and hose are fully intact.

Codes P0171/0174 are still firing sporadic when driving fast (and ONLY when driving fast) and GO AWAY IN THE MIDDLE of a drive. I tried a couple of high-RPM starts as well as WOT's - SES only comes on when cruising > 70.

I also found more issues with the cooling and HVAC. The hollow bolt is leaking a little, about an inch of coolant per 100 miles. I recreated the leak with a pressure tester and have replaced the rubber hose portion with a piece of brand new fuel line. It's still leaking under pressure though. The hose clamp appears to be in working condition but I change it on the weekend just to be sure. What size of a hose should I attach to the hollow bolt?

I also noticed that when the A/C is entirely off, there is a really strong ventilation going through the foot vents. I have never noticed that before and it's really annoying. Is that normal?
 
#154 ·
Still no luck. Only thing that was sounding like a vacuum related issue is a slow pressure relief (like slowly getting the air out of an air mattress) when I switch the car off on the right side of the intake manifold by the power steering pump. However, the center line, elbows, and hose are fully intact.

Codes P0171/0174 are still firing sporadic when driving fast (and ONLY when driving fast) and GO AWAY IN THE MIDDLE of a drive. I tried a couple of high-RPM starts as well as WOT's - SES only comes on when cruising > 70.
That all points back to a vacuum leak. Once those codes are stored they should stay stored for at least 3 ignition cycles. Remember, your highest vacuum is at idle. More throttle = less vacuum. At WOT you will have zero vacuum (or very close to it).
 
#155 · (Edited)
I freaking hate that piece of junk - every time you fix something, something worse happens. /rant and my apologies.

After switching out the coolant surge tank last week, I spend the better part of the afternoon yesterday and today's morning replacing the dry-rotted hoses and old weak hose clamps of the cooling system. We let it cool down for a couple of hours, pressure tested it - it failed miserably. We rechecked all hoses/clamps but couldn't locate the problem. Pressure tested it again and this time we saw a steady dripping of coolant by the mid-engine and through the lower splash shield.

It was too dark to diagnose the mid-engine leak (crossover and gasket have been repaired in January). However, following the leak into the splash shield revealed something appearing to be a micro-fracture at the upper left radiator body (see picture taken from passengers side radiator top just left of the metal mesh (condenser? heat exchanger?) it was dark so the quality is pretty bad). Am I correct in assuming this is another rather expensive repair?

Auto part Helmet Serveware Metal


The whole never-ending problems and expensive repairs put my friend over the edge, they're dropping the car. The thing has been sitting in my driveway for almost a month anyway but what I am asking myself is: is it worth repairing or is it time to drop that POJ?


EDIT: After checking alldatadiy, it could be just a plastic tank that is attached to the radiator: http://www.amazon.com/ACDelco-52491...r=2004|2004&carId=003&n=15684181&s=automotive

But you guys probably can confirm/reject that.
 
#158 ·
A note on replacing side tanks as opposed to the whole radiator: That radiator is aluminum and is at least 10 years old (we're still on the 2004 ?). End tanks are sealed with bent aluminum fingers (see your picture) and formed O-ring type seals. If you're set on end tanks only, have a radiator shop do it.... please.

In our (Seville-Devile) HVAC systems, when you turn OFF the A/C the system will continue to passively ventilate the car and also try to maintain the set temperature. The cars have flow-through ventilation and it operates - either active or passive - all the time. A trick is to turn the temps down to 60 (summer) or up to 75 (winter) before you shut OFF the system.

The rear flow-through vents are flapper valves under the trunk carpet sides, down in each lower rear quarter fenderwell.
 
#159 ·
I have not had to replace a radiator in many, many years so I'm not all that familiar with prices, but I swear I have heard guys mention prices less than half of what you are quoting.

Just a few.
http://www.radiatorexpress.com/part....y=19&subcategory_id=RADIATOR&stepCompleted=5

http://www.radiatorswarehouse.com/item.list.php?category=39750

http://www.autoradiators4less.com/home.php?cat=1103

And a whole lot more.
https://www.google.com/search?q=aut...s=org.mozilla:en-US:official&client=firefox-a
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top