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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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#2 ·
Re: [?] P0174 on a 04 Deville

That's a 2004 ignition system - The piping connector indicated is the "clean air" supply for the PCV system - that particular connection will not cause lean mixture codes - only the vacuum side of the system - and that comes out of the right (rear) cam cover and snake around to a nipple at the tunnel in the front (passenger0 end of the intake manifold.

P 0171/0174 lean mixture codes are caused by vacuum leaks. Get a mechanic's stethoscope and start searching. Look for plenum leaks. Google "cadillac forums northstar manifold plenum" or something close. It's the rubber/steel connector between the throttlebody and intake manifold. Many pictures/diagrams in my albums. The Community tab ^^^, albums, the red Seville.

His car has its own built-in code system (I think). Use the sticky ^^^ post "How to pull codes" section for the car, year, model. Use the link with "obd2" in the address to get to the Master Index of code definitions. Be sure to post whether each code is Current or History - it makes a difference.

Gas mileage - check the Fuel Pressure Regulator nipple and vacuum line for the presence of raw fuel. ANY fuel there is cause for replacement.

(Your 1999 is a VERY different engine from his 2004 ....................)
 
#3 · (Edited)
Re: [?] P0174 on a 04 Deville

That's a 2004 ignition system - The piping connector indicated is the "clean air" supply for the PCV system - that particular connection will not cause lean mixture codes - only the vacuum side of the system - and that comes out of the right (rear) cam cover and snake around to a nipple at the tunnel in the front (passenger0 end of the intake manifold.
Thank you so much - one more question if I may: is it normal that the connector is slightly greasy/oily? I observed some brown substance on both, the hose and the metal connector.

P 0171/0174 lean mixture codes are caused by vacuum leaks. Get a mechanic's stethoscope and start searching. Look for plenum leaks. Google "cadillac forums northstar manifold plenum" or something close. It's the rubber/steel connector between the throttlebody and intake manifold. Many pictures/diagrams in my albums. The Community tab ^^^, albums, the red Seville.
Will do - lots of very helpful pictures. Do I have to use a stethoscope or can I try the carb cleaner can spray trick? I seem to remember that the success of a stethoscope is closely tied to one having a rather quite garage and good ears - I lack both.

His car has its own built-in code system (I think). Use the sticky ^^^ post "How to pull codes" section for the car, year, model. Use the link with "obd2" in the address to get to the Master Index of code definitions. Be sure to post whether each code is Current or History - it makes a difference.
Sir, no offence intended but ... I really don't understand why in every answer on this boards refers to this link. We (I) may be amateurs in car mechanics but that doesn't mean that we did not already follow that procedure to the letter. I once had the same issue in my Seville, the SES light came on with no code being fired/displayed. That was exactly the reason why I bought the external code reader.

The on-board built-in code reader is merely showing a memory seat system code as written above. The P0171/0174 code is only retrievable with an external OBD-II reader. The way I am catching those codes since my first time on this boards is: activate all code display, capture a video with my smart phone, and assess the information at my desk by playing the video. That way no potential code gets lost. Anyway, I called him up to capture a video as well, here's the result:

MSM B1860 H - driver lumbar vert sensor circuit malfunction
MSM B1850 H - driver lumbar horiz sensor circuit malfunction
PCM P1585 C - cruise control inhibit output circuit - This one is new and wasn't there yesterday.

Gas mileage - check the Fuel Pressure Regulator nipple and vacuum line for the presence of raw fuel. ANY fuel there is cause for replacement.
I assume the FPR is the little silver silver distributor thing that says made in germany?
 
#5 ·
Re: P0174 on a 04 Deville

I repeat, I capture a video/pictures on my phone for all codes so that it does not matter how quick they fly by. Since there are two different code categories, I guess he selected all codes. I am sure that I did.

Anyway, when I tried to locate the FPR today, I made an observation. The hose identified by Submariner409 as "clean air" supply for the PCV system was not only cracked as shown by my picture yesterday but totally cracked in two (rubber elbow and plastic hose where physically separated - leaving about half an inch of empty air in between) on the other side (see picture 1):

Auto part Fuel line Engine Pipe Vehicle


About half an inch of the of the plastic pipe remained in the rubber elbow. The rest was cut off clean and pretty much obstructed by the bigger hose above it. IMHO this would also explain a slight whiff of exhaust-like smell in the Deville from time to time. The friendly auto part store next door provided us with about a foot of thick rubber hose (it says fuel vapor on the hose) and I built two new connectors: one elbow

Auto part Fuel line Pipe Engine Automotive fuel system


and one hose for the part connecting to the front:

Fuel line Auto part Pipe Automotive fuel system Gas


I put the adjusted hose/piping in and the car started up purring like a car. No rough idle, not the slightest shake, and the SES light did not light up. However, since he had to drive to me, the engine was already hot so I might celebrate too early. :hmm:

Strangely for me was to learn that the elbow and plastic tube had some goo in it, it looked like dirty oil and fuel. If this was just a clean air intake, I assume this shouldn't be the case?

Could the total separation have been the reason or am I'm not getting off that easy?
 
#7 ·
Re: P0174 on a 04 Deville

The PCV system is subject to some really nasty oil/moisture/acid vapor movement. When you shut down or when piston ring blowby (extreme power demand operation) exceeds the flow rate of the PCV orifice (no rattle valve in your particular engine) there will be some reversion of crankcase vapors > back into the atmospheric side of the throttlebody - leading to some goo and slippery snot in the lines. Normal. Along with your annual throttlebody cleaning maintenance you might want to soak those 2 PCV lines in mineral spirits to clean them out a bit.

EVERY one of these engines should have a vacuum line/connector inspection occasionally - PPPPPP (Prior Planning Prevents Piss Poor Performance)
 
#8 ·
Re: P0174 on a 04 Deville

Thanks, Submariner409 and Ranger. He drove the car for about 30 miles today and the SES light did not come on at all. I also observed a strange starting/idling though - just after start the car is idling at 1200 rpm which goes down a notch by the second until resting stable at 700 rpm. We'll clean the TB as instructed tomorrow. Let's see how that goes then.

One tiny question though: I am not putting the utmost trust in the new hoses I built yesterday in the dark with a carpet knife. So when I checked my work today at daylight, he had the car running and switched it off while I inspected the stuff. The second he turned it off, I heard a noticeable hiss from around the PS reservoir or coolant reservoir (upper passenger side of the engine compartment). It stayed there for about 10 seconds. Is that normal?
 
#9 ·
Re: P0174 on a 04 Deville

Your cold idle is normal. 1200 RPM at cold start for about 40 seconds. Once the air pump shuts down it drops to about 900. Then at a predetermined temperature (I forget what that is) it will drop to 650.

No, the hiss is not normal. It could be the manifold over pressurization valve not sealing. Has it backfired recently? The valve (spring loaded flapper door) is in the tunnel behind the P/S pump.





P.S.
This is for a pre 2000 engine as in your profile. Not a post 2000 as in your title.
 
#10 ·
Re: P0174 on a 04 Deville

Again, thank you Ranger. I have cleaned out my TB today as well as the vacuum lines. I would suggest that the guides here are - despite the experts probably being used to that - updated with a comment or two on the first minutes after a TB clean being quite rough. Today, the SES light blinked for about 8 seconds and the owner was almost having a stroke because of that.
 
#12 ·
Re: P0174 on a 04 Deville

After any throttle body cleaning or chemical sprayed into intake you should start the engine as follows. Turn key to "on", press throttle pedal to floor, crank engine until it starts, release pedal. If the engine immediately stalls then repeat. This will prevent back fires and rough running from pooled chemical.

Vernon
 
#17 ·
Re: P0174 on a 04 Deville



Exactly the point of holding it at full throttle after flooding the intake with flammable cleaner while cleaning the throttle. The idea is to let the engine start on and consume all of that "fuel" before adding unnecessary gasoline to an already "fuel" saturated intake and flooding it worse. The high rate of airflow at wide open throttle also picks up any pooling fluid and carries it into the cylinders instead of letting it sit evaporating and flooding the engine for several seconds, as this one did with the friend freaking out about it because he thought it was broken or ruined etc. Doing it twice I said will take care of the rest if you've actually got enough cleaning fluid in there to kill it on the first attempt when you instinctively remove your foot from the throttle as the engine is revving full tilt and it dies due to still flooding.

Clear Flood Mode is almost universal for electronic fuel injection, all makes and models. It's also very useful for starting an engine who's ECT sensor is broken and causing -32* fuel enrichment. Anytime you're cranking a EFI engine a lot and it doesn't start try holding the pedal to the floor for a while. It doesn't work for crap on the older vane air meter Mazda's and Fords though, you have to pull the full pump or injection fuse on those. They keep spraying fuel as long as the vane air meter door is being pulled open.

It's really not a big deal and this is the way I start every engine I clean a throttle on, it starts right up and on to the next task, like relearning the idle speed.

Vernon
 
#14 ·
Re: P0174 on a 04 Deville

Hehe, I can imagine that may have put you in the OMG, WTF did I do mode. I usually stuff a rag back in the TB and just into the manifold to sop up as much of the solvent as I can after the TB cleaning to prevent that. Just about as far as I can reach with my finger (not doable on all engines). You could also use a brake bleeder to suck some out or just block the throttle plate open for an hour or so to let it evaporate if you are concerned about it. More than one way to skin this cat.
 
#15 ·
Re: P0174 on a 04 Deville

Good morning - personally, I was not too concerned - my Seville trained me well in that regard. I can confirm that there was a lot of cleaner in the system - the Deville has 130k on its back, all city, and the TB was never cleaned (according to the owner). There was a lot to clean to say at least. However, I was amazed how easy the procedure was though, totally non-Cadillac :)

I just recalled another question I wanted to burden you guys with: I observed that the gas pedal pull line was sitting tightly in that little throttle rotor but the cruise line (?) was sagging a lot. Could that cause the other code with the cruise control? PCM P1585 C - cruise control inhibit output circuit
 
#16 ·
Re: P0174 on a 04 Deville

No. I believe that is the way it is supposed to be. The PCM can only detect faults that are electrically monitored, not mechanical things. "Cruise control inhibit output circuit" sounds like it might be referring to the disengage switch on the brake pedal. Does the CC work?
 
#18 ·
Re: P0174 on a 04 Deville

I didn't know the open throttle trick but will add it to my checklist. One never stops learning :thumbsup:

Ranger I asked him to check and sure enough, cruise control is not operational. The light on the steering wheel switch comes on but that's about it. I guess this is an repair attempt for yet another day.

On an off-topic note: how hard is DIY brake service for the rear? I have seen some gorgeous brake rotors in submariners album. Our local mech quotes $270 for back rotors and pads.
 
#19 ·
Those are EBC Ultimax slotted rotors, and RedStuff ceramic pads. I have them on my car as well, and they are EXCELLENT brakes. Smooth, powerful, quiet, and low dusting. All 4 corners will cost you just under $500, shipped, from www.placeforbrakes.com.

You can skip the slotted rotors if you don't plan on doing any quick/repeated stopping from "questionable" speeds.

Also, I wouldn't recommend a rear only brake upgrade. Either front only, or all around.

DIY brake jobs are about as easy as it gets. The only specialty tool you'll need is a brake cube (~$10) to turn in the rear caliper pistons (pushing them in will destroy the parking brake/self adjusting mechanism). Or, you could use needle nose pliers.
 
#25 ·
sporadic SES light and exotic codes

Hi guys,

I was bound at work, so I was unable to follow up on my freind's caddy for a little bit. Sure enough, new problems arose. He was complaining about sporadic (NOT! flashing) SES lights at long trips lighting up within the first five minutes of the drive and disappearing after a gas stop. He claims there is no dashboard message and I pulled the following codes (bold ones have not been there 4 weeks ago):

AMP U1064 H - Loss of Communications with DIM
AMP U1128 H - Loss of Communications with IRC
IPM B0429 C - Temperature Control #3 rear circuit range/performance
IRC U1016 H - Loss of Communications with PCM
MSM B1860 H - Driver Lumbar Vert Sensor Circuit Malfunction
PCM P1585 C - Crusie Control Inhibit Output Circuit

If I understand what I read at this boards correctly, none of those codes should fire an SES?

PS: Another anomaly - while cycling through the cars menues, the transmission fluid has only 58% life left. He only remembers of having the master cylinder and brake fluid replaced. Is this someting that needs rather immediate action?
 
#28 ·
Re: sporadic SES light and exotic codes

......... and it depends on which one of the Devilles in your previous posts we're trying to diagnose.

The Cruise inhibit code might pertain to the switch on the brake pedal arm - that allows/drops out cruise control depending on brake medal movement.
 
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#32 ·
Re: P0174 on a 04 Deville

Remember - the rear caliper pistons do NOT compress back into the caliper - they must be screwed back in and the piston face indents aligned with the pad backing plate indents. It's part of the parking brake ratchet adjustment mechanism.

You will need the proper torque values for the rear brake parts bolts. Brake pin lube.

www.alldatadiy.com - Chilton and Haynes manuals are far too generic.
 
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