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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.
 
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#99 ·
.......... talk about over-thinking a simple procedure ........... and we're NOT trying to maintain pressure anywhere during a purge line flow test: That hollow bolt/nipple sits at a high point on the discharge side of the water pump - into the water crossover. IF the hollow bolt/nipple and the rubber/plastic line is clean/clear (depending on car model) then the water pump flow discharge itself is what we want to see - maintaining system pressure for a simple test has no bearing on the outcome.

Pull the hose off the surge tank, idle the engine, and watch it dribble into the open surge tank neck. If the hose/plastic line is toast, replace it with a proper sized length of rubber fuel line (has a braid jacket, will hold far more than system pressure) from any parts store.
 
#101 ·
Ranger, I am probably totally guilty of over-thinking a simple process but I am not crazy enough to remove the cap while coolant is hot. Anyway, I have checked the flow, it's still a steady, significant flow of coolant. The Deville had no issues holding its temperature at straight 12 o'clock. Coolant level was lower after a 15 mile test drive but is now stable since two days at max cold mark. However, the bubbling sound is back - how long does it normally take to bleed the air out - assuming that the cooling system had LOTS of air in it? The car is normally driving around 10-15 miles a day.
 
#103 ·
Yes, as I said its like someone gurgling lysterine in the engine compartment. It usually goes in sync with acceleration and stops as soon as I let go of the pedal.

I have checked all liquids today, no issue with any of them all but oil on the spot (half a pint fixed that) and even the trans fluid looks ok (despite the dash display). I'll have that changed as soon as I find a shop not just flushing it, as Sub pointed out. Strangely even the dealer wants to just connect it to a fluid exchanger machine and just lets it run for a while ($189 and still no pan drop). It's time that Manic opens his shop close by.
 
#104 ·
Personally, I don't like fluid exchange machines. I prefer to drop the pan and clean any debris as well as the magnet, but then that takes a little longer. If it where not my car and I was charging for the service, I'd prefer the quicker easier method. That said, I'd figure out this gurgling and overheating issue before I'd spend any more money or time on it. Something is definitely not right.
 
#105 · (Edited)
Overheating seems to be solved - at least in my amateur mind: the last coolant fill was in January, when the crossover was repaired. We both did not check the coolant thoroughly enough since then and eventually it slightly overheated (no code or anything really significant like with my old Seville "ENGINE OVERHEATED", just the needle at 230F on the "SubMariner Scale"). It was spotted almost immediately (within 5-10 minutes I'd say - I am paranoid after my Seville stranded me last year). Thanks to the excellent advice on this board, I confirmed a clogged hollow bolt and no fluid movement through the purge line. After this was fixed, the needle is glued to 12 o'clock. There was not too much coolant missing, maybe around a soda can. During the cleaning process of the hollow bolt we identified a disabled coolant level sensor which pretty much explains why the car did not complain about lacking coolant. Now there is a steady stream of coolant through the purge line and after an initial slightly lower coolant level, it sat straight at the full cool marking for about a week. I'll be away for two weeks and will re-check then.

The gurgling - I have no idea. I am constantly checking fluids now when I have the car near me but all looks ok. Regarding the vacuum leak that lead to this thread, I carefully sprayed throttle body cleaner around the plenum last weekend and moved it around a little with my fingers but did not spot any change in idle RPM. I did however, spot a semi wet area just where the underbelly of the plenum meets the intake manifold on the metal of the block. However, the connection to the brake booster is rather loose, the vacuum hose connects to a piece of plastic with no clamp securing it. Furthermore, the plastic socket spins around easily. This was one spot that Manic pointed out a while ago as potential problem area. Will try to check it more thoroughly when I have the next chance to do it.

The rough idle at the first minute after a cold start is confusing. I think it was Manic that provided me with a checklist. The MAF seems ok but the MAP did not behave as it should have. I used an OBD reader with live data capabilities and found out that in the first 60 seconds after a real cold start, the MAF is sending "0 gr/s", while the MAP is all over the place (between 0 and 90 KPa). After approximately 60 seconds, the MAF suddenly sends data unequal to zero and the car instantly purrs like a cat with RPM are falling from 1200 to 675. I'd assume the MAF has some kind of warm-up period.

I'd appreciate your thoughts as I do fear doing exactly what Ranger pointed out: throwing parts at a terminal car patient.
 
#106 ·
Two weeks and a couple of hundred miles later in the Texan heat: the cooling system is reasonably stable. When I checked yesterday, the coolant was around 2mm below the max cold fill line. Temperature is stable with minimal movement straight or very close to 12 o'clock.
 
#107 · (Edited)
There's a LOT of sensor stuff that is not monitored or controlled during that normal 1200 rpm fast idle startup. Some sensors aren't even monitored until the systems go closed loop at somewhere between 110 and 160 degrees coolant temp, depending on ambient temp at startup.

1200 or so rpm for 20 - 50 seconds, 900 or so rpm for a little while, 650 +/- rpm idle after a little while. THEN stuff settles out.

If your cooling system is tight, that apparent coolant level will rise and fall (cold) about 6mm depending on ambient temps, but there should be NO actual coolant loss for at least 18 months.

Anal gearhead maintenance: Every April and every October, engine cold, I siphon off exactly 2 quarts of coolant and replace the exact amount with fresh mix - 50/50 coolant and distilled water - so every 6 months there's a fresh infusion of coolant additives and corrosion protection. I do the same drill, at the same time, with the P/S fluid and the brake fluid reservoirs.
 
#108 · (Edited by Moderator)
There's a LOT of sensor stuff that is not monitored or controlled during that normal 1200 rpm fast idle startup. Some sensors aren't even monitored until the systems go closed loop at somewhere between 110 and 160 degrees coolant temp, depending on ambient temp at startup.

1200 or so rpm for 20 - 50 seconds, 900 or so rpm for a little while, 650 +/- rpm idle after a little while. THEN stuff settles out.
Thanks for the reply Sub! My problem is that in that very first minute the car is not generating power. Basically, to avoid misunderstandings because of my funny English, when I try to drive away without waiting a minute the car is taking the gas petal very hesitantly and driving extremely rough. At the instant, the MAF kicks in (and sends data), it drives like a star.

On a side note: my coolant sensor is stuck in the reservoir because of some stop leak residue (compliments of the former owner - leaking crossover gasket was fixed after the car was bought by my friend). Is it possible or advisable to clean the otherwise perfectly alright tank or should I get a new reservoir in any case?
 
#109 ·
If you want to go through the exercise, drain the cooling system (again) and remove the surge tank. Plug the holes, use some dishwasher liquid detergent (nasty stuff), some water and make like the bartender shaking James Bond's martini. Rinse well.

The level sensor reed switch (not the float) - in the bottom of the surge tank - is replaceable (if you can find one). Otherwise, a new reservoir with sensor is about $60, shipped, from Amazon.

EDIT: Unplug the darn sensor and check the coolant level visually during your usual semimonthly underhood checks.
 
#110 ·
Spend the whole day yesterday washing the surge tank (sensor works now - thanks Sub), cleaning the MAP (idle RPM dropped by 100 to 650, MPG's increased by 1.5 - thanks ManicMechanic), rotating the tires, and desperately trying to find the vacuum hole. I tried to do what Ranger told me: to massage the plenum while spraying an aerosol around it - my problem is it didn't work. My plenum has a metal clamp around it in the middle and it does not move a millimeter. No way to massage it with that clamp onß Is it safe to remove it and try again or do I cause much more trouble when I do?

Anyway, I can conclude that I hate the Caddy and the Northstar in particular. Today I received word that the car is acting up in idle and very low RPM's by beeping and displaying "low oil pressure - stop engine". I have already read around here and learned that this is a kind of a common fault. I was annoyed, so when I got to it and against my better knowledge, I stepped on the gas and the message disappeared instantly - however came back at low RPM's. Is there an easy way to determine if it's just the switch or something major?

According to rockauto, a new ACDelco D1836A Switch Assembly is only around $8. I read in another thread that it takes about 2 hours to change, although it looks fairly straight forward (even to me) on the pictures that Sub provided. Is there some obstacle making a rather simple screw-out and new part in so difficult? Am I right in assuming that we will loose all that brand new oil that we put in a month ago when changing the switch?
 
#112 ·
Plenum has a rubber bellows (flex area to compensate for temp changes) next to the band clamp - that's where the leak shows up.

See that rubber bulge next to the clamp ??? The lower part of that is what tends to crack.
 
#113 ·
I tried to do what Ranger told me: to massage the plenum while spraying an aerosol around it - my problem is it didn't work.
Chances are the plenum duct is good. If it where leaking you'd have a P0171 & P0174 code.

Today I received word that the car is acting up in idle and very low RPM's by beeping and displaying "low oil pressure - stop engine". I have already read around here and learned that this is a kind of a common fault. I was annoyed, so when I got to it and against my better knowledge, I stepped on the gas and the message disappeared instantly - however came back at low RPM's. Is there an easy way to determine if it's just the switch or something major?
Unless you (or someone else) removed and reinstalled the crankshaft damper, it's always the switch.
 
#114 ·
Chances are the plenum duct is good. If it where leaking you'd have a P0171 & P0174 code.
I have both every now and then, especially when going above 70 mph. They go away quickly in normal city driving. Is it safe to remove the clamp for better access or am I running danger of damaging the plenum then?


Unless you (or someone else) removed and reinstalled the crankshaft damper, it's always the switch.
I had him check all the garage receipts. The only major thing being repaired in the general vicinity was the coolant crossover gasket. The service records (if provided completely) of the previous owner do not mention any repair regarding the harm balancer,
 
#115 · (Edited)
You can't remove the clamp - it's captive.

More pictures in www.rockauto.com, the car, model, year, engine, intake coupling. The Dorman sells for about $16 - with all 8 manifold seals. A GM dealer wants $7 apiece for the seals (2002 price), $45 for the plenum. In RockAuto, click the INFO tab in the Dorman text line - you can see 3 different views of a plenum - and the seals.

Just in case - That plenum steel plate has 3 captive nuts - welded on - they receive the 3 long bolts that go all the way through the throttlebody - so there's a bit more disassembly required than just the intake manifold and fuel rail. Convince "your buddy" that he needs a subscription to www.alldatadiy.com.
 
#116 ·
The subscription is not the problem Sub - I had one since the Seville. However, having a combined four left hands is and a very incomplete set of tools doesn't help either. :hide:

I have ordered one ACDelco D1836A Switch Assembly as well as an oil pressure switch socket, should be at my door step by Thursday.

BTW: ACDelco has a promotion going on at Amazon with 25% additional rebate for ACDelco Spark Plug Wire Sets, ACDelco Engine Air Filters, ACDelco Oil Filters, and ACDelco Cabin Air Filters.
 
#117 ·
I had a couple of spare minutes today and checked all fluids, hoses, etc. - oil cold was slightly under the middle of the dashed area, hot it's spot on the middle. Coolant is sitting straight at the cold max mark since 3 weeks. I did a 20 miles test drive. No issue, error, code, whatsoever. I double checked that the oil error bulb is still operational (I know paranoid) but the car is performing as if nothing ever happened. That thing drives me crazy.

One thought, maybe totally stupid: the day before the car complained about the oil pressure, we were liberally spraying throttle body cleaner around the plenum, intake manifold and vacuum hoses to identify the leaks causing the lean codes. Could this upset the pressure switch? Even more stupid question: when I checked the brake booster vacuum hose, it smelled like gas. Is that normal?
 
#118 ·
One thought, maybe totally stupid: the day before the car complained about the oil pressure, we were liberally spraying throttle body cleaner around the plenum, intake manifold and vacuum hoses to identify the leaks causing the lean codes. Could this upset the pressure switch?
No.

Even more stupid question: when I checked the brake booster vacuum hose, it smelled like gas. Is that normal?
No.
 
#121 ·
A brand new plenum duct from Amazon just arrived and we'll (attempt to) put it in over the weekend. Let's see how that goes. In preparation, I test drove the Deville today and two issues still concern me:

  1. When just cruising at road speed (no hills/slopes/valleys) holding the gas pedal steady, I frequently had to readjust. It felt like the car not delivering steady power and I had to step on the pedal. Usually it kicked down afterwards and delivered an adequate level of perfomance. The TB looks clean and responsive having had its last clean less than 1500 miles before.
  2. This gurgling sound is still there and drives me insane. At almost every acceleration after a stop, red light or traffic, the car is going through its listerine. Unfortunately it's only noticeable under load, when I sit in front of the car just gently pulling the throttle cable, nothing happens. From inside the car it seems to originate from the mid engine section towards the firewall. Can it be a clogged heater core (although no one of us ever had to use heat on the car), an A/C moisture outlet (the A/C is pretty much always on since March) or [please insert random good idea here]? I'd appreciate any pointer on anything I can check.
 
#122 ·
See how it runs after the plenum duct change.

Gurgling is NOT good. One thing I think we can all agree on is that it's coming from the heater core. That is almost 100% positive. The only question is why. IF you have checked the purge line and are 100% sure it is clear, then the only other logical explanation I can come up with is that air is being introduced to the cooling system.
 
#123 ·
Ranger, I have checked all accessible parts of the coolant system:

- coolant in the reservoir stays more or less at the same level - there is an almost unnoticeable loss but on the other hand I spill a tiny amount every time I check the purge line.
- purge line has a steady, gentle stream - I noticed a lower pressure after things have settled. At first it was shooting out of there, now it's streaming steadily but calmly
- after carefully inspecting the reservoir cap, I noticed that the inner (lower) rubber seal is extremely porous and falls off on finger contact. There is still rubber present but the edges are quite flaky.
- the car's temperature stays stable at 210, a tad over the middle of the scale (12:02 o'clock) regardless of whether it's a short drive or a traffic jam in TX heat of 105F
- when I unclogged the purge line, I noticed small particles that looked like a mix of rust and stop-leak - we have never flushed the heater core. According tho the bill, the coolant was just changed at the shop when they repaired the crossover gasket.

What would be a sensible approach? Buy a new cap since it's less that $5 and hope for the best? Flush the core? Do a block test?

Since my coolant sensor was having issues, we invested $10 in a bluetooth gizmo and an app for my mobile phone. It constantly monitors the car's state as well as error codes. I have set an audible alarm for 232F coolant temperature to avoid having an issue coming up when someone is driving who doesn't has the eyes glued to the temperature. The only thing coming up (a week ago) was that:

Map Electronics Gps navigation device Line Technology
 
#124 ·
This one has me stumped. Coolant flow from the purge line rules out a clog. Pressure is irrelevant. No coolant loss rules out a leak and no overheating would rule out, or at very least, lean away from a HG failure, so a block test would most likely come back negative. Likewise, no overheating would rule out a bad cap. I can't imaging how there is air in the system causing the gurgling or where it could be coming from.
 
#125 ·
When thinking about the thermodynamics of the coolant system, the only theory I was able to come up with is a micro/stress fracture somewhere in the system. Too small for coolant to be pushed out, even under pressure but small enough to suck air in when the antifreeze contracts at cool down. Would fit the symptom of it NOT gurgling when the car is started cold but only happens when the car was hot, had time to cool around 2 hrs, and is started again. But this is maybe too constructed for the real world and will be pretty hard to diagnose since fluid loss would be minimal. Maybe a good splash of UV dye may help?
 
#126 · (Edited)
Kicker is, the possible crack would not allow air to enter the system until the engine had cooled to at least a few degrees below ambient temperature, and even then the surge tank pressure cap has a built-in vacuum relief valve that opens at only 1 or 2 inches of vacuum - if the cooling system went into any more vacuum than that the (non-reinforced) hoses would collapse.

If you even think that the pressure cap rubber washers are falling apart, get a new cap. It's entirely possible that the engine is warming up, not holding a full 18 psi, and maybe some coolant is blowing out the leaky cap seal.
 
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