: P0171 - P0174



Nickcruffin
05-31-05, 07:39 PM
What in god's name would cause a P0171 and P0174 code. I have replaced everything in the system. Including Bank one and two O2 sensor, Map, Maf, TPS, All the injectors, and fuel pressure regulator. This is driving me nuts. See my other postings.



I am ready to shoot the damn thing.

mcowden
05-31-05, 10:19 PM
Whoa, take it easy there. With the engine running, are the codes current or history? If they're history, then forget about them. It happened in the past and they're nothing to worry about. If they're current, then it's saying the mix is running lean on both sides. You may have a vacuum leak again. Start looking at the intake gasket you replaced and listen for any hissing. PCV valve and hose OK? Plastic intake cracked? Brake booster line connected? Stuff like that. What symptoms does it have now? Running strangely?

It's driving you nuts because you've had lots and lots of bad advice in the past. At least, that's what it sounds like from your earlier postings. It's time to settle down and tackle these things one at a time. The car will run fine once it's properly diagnosed and properly fixed.

Ranger
05-31-05, 10:45 PM
This is not complete but I'll touch on the high points from the '97 manual.
IMPORTANT
An improperly installed air cleaner or a distorted/missing intake air duct may cause this DTC to set. Ensure air cleaner assembly/IA duct is installed correctly and that there are no kinks, folds or damage to the IA duct or possible debris in the air cleaner assembly or the MAF sensor inlet screen (air flow straightener) that may distort the air flow.

Step 6
Visually/physicaly inspect the following items.
Vacuum hoses for splits, kinks and proper connections.
TB, intake manifold and EGR valve for vacuum leaks.
PCV valve and/or system for leaks including a loose or missing oil fill cap or dipstick.
Contaminated fuel.
PCM and sensor grounds are clean, tight and in proper locations.
Air induction system after MAF sensor for vacuum leaks.
Engine mechanical failure.

If the problem was not found in the above areas go to step 7

Step 7
Visually/physicaly inspect the following items.
Exhaust leaks, missing or loose exhaust hardware.
HO2S are installed correctly and electrical connector not contacting exhaust system or ignition wires.
Injector "O" rings

Hope this is of some help.

Nickcruffin
06-01-05, 07:37 PM
To day it was the P0131 code in Current. I erased the the P0131 code about 4 times today and now it is not even in History. the P0171 & 174 codes are now not in history either. And, the car is running strangley. It looses power but now only for short periods of time. gas milage is down but not as bad as it has been.

Ok i will look at everything, again.

Nickcruffin
06-02-05, 08:34 PM
Another day and the P0131 code again and again. Car runs ok then slugish then ok ?????????

mcowden
06-03-05, 12:21 AM
The P0131 code is the oxygen sensor. I mentioned before that I think you should replace it. I still think you should replace it. I know you've done it before, but if the system is running lean, it could burn up the sensor.

Before you replace it, though, you need to find the source of the vacuum leak. It may be the intake gasket area since you mentioned previously that it was a problem. Is the brake booster line connected properly? Any hissing sounds under the hood? How about when you take off the appearance cover? You'll need to check for this either while the sluggishness is occurring at idle or somehow cause it to occur by jiggling things a bit. Does the intake move? PCV valve and hose OK?

It could also come down to a MAF or MAP, I suppose, but there should be a code related to that. Have you ever cleaned the EGR or throttle body?

Nickcruffin
06-03-05, 11:19 PM
I cleaned the throttle body when I had it off to replace the manifold. Today the 131 is in history and so is 171 174. Car keeps running and now it is running ok.

No hissing, Break booster line is connected no splits, never cleaned the egr. Where is the EGR on a 4.6??

zonie77
06-04-05, 10:16 AM
We had one that had the insulation on the wires INSIDE the harness come off and caused intermittent problems. That was on the intake harness (injectors, MA, etc) open the plastic covering and check, especially near the connectors.
It caused strange problems.

Nickcruffin
06-04-05, 02:28 PM
now that is some help --- i will start looking now. Thanks

Nickcruffin
06-06-05, 02:23 PM
Still nothing --- engine now will not start.

pugel
07-16-07, 08:53 AM
I'm getting P0171&P0174 on my 2000 Deville "Y" N* too.
When cold, it idles perfectly, vaccuum guage shows proper vaccuum and it doesn't hiss.
When hot, it idles roughly, vaccuum guage shows loss of vaccuum and it hisses.
I tried most tricks I found in this forum (cleaned MAF sensor, changed PCV valve, carefully tightened intake manifold, looked for vaccuum leaks)
What would cause it to only do this when hot?

ewill3rd
07-16-07, 12:38 PM
2000 to 2005 are prone to leakage at the "plenum".
I recently posted some pictures to a topic recently. Maybe someone could link it up?
Basically there is a boot between the throttle body housing and the intake manifold. They tear at the bottom where you can't see them.
A can of brake clean or carb cleaner will usually verify it, spray at the base of that boot with the engine running, if it is leaking the idle will be affected and it will be noticeable. Sometimes you can even hear the noise.
It is fairly easy to replace but can be hard to find if you don't know it is there.

http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/112014-p0174-code-driving-me-crazy.html

pugel
07-17-07, 08:33 AM
Carb spray showed that's where the vaccuum leak is. Thanks. How do I replace the boot? Do I have to remove the intake manifold? Any installation tips would be appreciated. Where did you get the replacement parts? Rockauto doesn't list it. Is it a dealer only part?

ewill3rd
07-17-07, 01:19 PM
Someone else might know how to get them, did you try gmpartsdirect.com?
You can also call Luke at 703-647-8670 and tell him you are a forum member and Bill talked to you about your problem.
You'll need a "plenum" and 8 intake manifold seals.
I think the parts aren't too expensive.

You do have to remove the intake manifold but it is pretty easy.
The hard part is getting the injector rail off and moving it out of the way.
He needs the last 8 digits of the VIN. We should have the parts in stock and he will give you a fair price for sure.

I'll try to get a chance to post some instructions or more photos.

segancz
01-17-08, 07:47 PM
Someone else might know how to get them, did you try gmpartsdirect.com?
You can also call Luke at 703-647-8670 and tell him you are a forum member and Bill talked to you about your problem.
You'll need a "plenum" and 8 intake manifold seals.
I think the parts aren't too expensive.

You do have to remove the intake manifold but it is pretty easy.
The hard part is getting the injector rail off and moving it out of the way.
He needs the last 8 digits of the VIN. We should have the parts in stock and he will give you a fair price for sure.

I'll try to get a chance to post some instructions or more photos.

I wish i read this post before i spent 3 hours looking for the problem i did a smoke test for a vacum leak and it didnt show up. Apparently once the car is running the viabration streches the boot between the throttle body and the planium and that was my problem.PS i also did the map and oxygen sensor checked the injectors and engine compression hell i even put in and reprogramed the pcm and that wasnt the problem!!!!!!!!!!!!!!!!!!!!!!!!!!

ewill3rd
01-17-08, 08:10 PM
Well at least you'll know next time... :D

Sorry to hear about your stress, but at least you got it fixed.

AlanSr
10-20-09, 12:09 AM
How much would this fix cost at a dealership?
Or do you guys recomend another mechanic shop?

I just started getting the rough ideling and hissing sound.
I can clear the codes but they come back a day or two later.

ewill3rd
10-20-09, 08:15 AM
Alan, how much it costs can depend on where you live.
Parts pricing and labor costs can vary from market to market.

I can ask one of my advisors what this usually costs out the door if you want but as I said it can vary greatly depending on where you live.

Submariner409
10-20-09, 08:20 AM
Bill,
I looked at Alldata and they have 2.6 hours for the manifold, nothing for the plenum, so I threw in another .5 for 3 hours @ $100/hr + $42 for the plenum and maybe $55 for the manifold gaskets = $400 ???????? Close ?????

Alan, Have you definitely localized the hiss to the bottom of the plenum coupling ?? #2 in the drawing. Click to enlarge.

AlanSr
10-20-09, 07:49 PM
Thanks for your responses guys!

No I haven't identified it yet but last weekend I pulled the cover off and checked all the hoses and didn't find any leaks.
but when it warms up it hisses real bad.

I am less than moderly mechanically inclined. I can change oil, trans fluid, and rear end fluid....and a few other minor fixes.
Would this be something out of my ability?

Submariner409
10-20-09, 08:22 PM
Subscribe your car to www.alldatadiy.com for one or more years. More than you can ever want to know about your car. That and the parts necessary will cost you about 1/3 of a dealer charge, it's not technical, and you'll learn a lot about the engine.

Pay attention to diagrams and torque settings, go slow, clean everything, and you'll be good to go. The Northstar intake manifold is "dry" - nothing involved except air and gaskets - no coolant passages. 20 nuts and bolts, and you get to check the starter motor connections (yes, it's under there) and manifold vacuum fittings.

No guts, no glory..........before you start taking things apart, find the source of the (warm) hiss.

AlanSr
10-21-09, 02:17 AM
Great!
Thank you very much.

I'll have to look into that.

kendro
01-20-10, 10:53 PM
I also have the P0171 and P0174 codes. I took to shop and had it checked for intake leak. None was found. They cleaned the injectors and the MAF. The codes were gone long enough to pass emissions, but now they have returned. Today, I was driving to work, turned my headlights off, adn the whole car hiccupped---clock reset to 12:00 and the gas gauge went to empty. The car did not die though and the fuel gauge returned to where it should have been. I checked the codes and got the B1552. After work I checked the battery cables--felt tight, but noticed a B1558 code. Later I disconnected/reconnected battery cables to ensure that they were properly tightened. Doesn't seem likely that the P codes were related to the B codes, but is it possible? Assuming the B codes do not return, what's next for the lean codes, ensuring that ALL hoses, etc. are checked for an air leak?

kendro
01-20-10, 10:54 PM
Forgot to mention I have a 98 Eldo.

Submariner409
01-21-10, 08:19 AM
Remove the engine beauty cover and track down all the plastic/rubber vacuum lines which come from and go to the throttlebody casting nipples. If one of the plastic lines is cracked/broken it may be replaced with an equivalent length of proper sized vacuum hose, available from the blister pack racks at any parts house. Check the EVAP solenoid hose connector and piping (under the driver's corner of the fuel rail area) - follow it to the EVAP canister - this system stores fuel tank vapors until the engine is at a steady state cruise and then the solenoid opens and the engine vacuum purges the vapors from the canister - you can understand the consequences of a vacuum leak here.........

The PCV valve (rattle can) is located in the passenger end of the rear cam cover, with a 1/2" line which runs down into the recess in the intake manifold, behind the p/s pump. Carefully disconnect that line, pull the PCV out of the grommet and shake it. If it does not rattle freely, replace it - $2.50, parts store. (2000(?)+ engines do not have a rattle valve - they use a fixed orifice.) The PCV fresh air supply line runs from the throttlebody upstream of the throttle butterfly to an equivalent fitting in the front cam cover. If any one of those lines is cracked/broken it will cause a vacuum leak.

ewill3rd
01-21-10, 08:48 AM
On a '98 typical sources of lean codes are:
Intake manifold gaskets
The backfire valve in the end of the intake
The backfire valve housing O-ring. You can twist the housing out and service the o-ring seal, it dries out and leaks. (it is hard but it will come out)
Vacuum lines (as stated above)
The vacuum solenoid assembly inside the car for HVAC mode door control. (if so equipped)

kendro
02-08-10, 02:31 PM
I took the 98 Eldo back to the shop to have it checked out. Since the p0171/p0174 codes have gone to history, the shop would not commit to what could be causing the lean code. They gave it the once over, but in the end recommended replacing 3 O2 sensors as "routine maintenance". Also, because the P0420 code for the catalytic converter is current, they recommended replacing that too. I read on a thread in this forum that the lean codes may be causing damage to the cat, so I do not want to replace the cat without finding the source of the lean condition first. The shop disagreed with this assessment, saying they did not think that lean conditions would cause cat damage. At this point I declined all the recommended services, which were $900+. Am I making the right decision or am I risking further damage by not replacing the catalytic converter now? The temp diff reading given to me was 30 degrees instead of the specified 75 degrees.

emsav8er
02-20-11, 01:28 AM
I got a check "engine light" and went to autozone for them to check it out. I got the code of P0171 - P0174. Drove it home and started checking things out. I disconnected the negative battery cable so to make the computer recheck everything. I have a K&N air filter and pulled the MAP plug just to check it out and clean it. I doing so, I noticed that where the air intake tube running between the MAP and the air intake had backed off the connection a little allowing about a .5 mm gap. I tightened it up, reconnected the battery, and drove it for about 15 miles and the "check Engine" light extinguished. Ta Da!!! Remember, the "check engine" light will not extinguish unless you clear it with a code reader or do it the way I did it. Patients patients patients.

Submariner409
02-20-11, 10:49 AM
I got a check "engine light" and went to autozone..... Remember, the "check engine" light will not extinguish unless you clear it with a code reader or do it the way I did it.

It's too bad that the 2005+ Cadillac code readers aren't built-in like earlier models. We don't need scanners, shops, and battery disconnects to read, clear, and store codes; it's all done on the dash board control buttons.

The SES light will extinguish and the code goes to History after 3 successful START-RUN cycles during which the offending Current code does not set. If the fault does then not occur for 30, 40, 50 or 100 successful START-RUN cycles (depending on module), it self-clears from History. I'd bet that the P0171/P0174 is still sitting there in History.

BTW, Your K&N filter may be the cause of your fuel mixture code problems - the .5mm air leak after the MAF notwithstanding. I believe your MAP is still in the top of the throttlebody casting.

thx4urm0ney
02-16-12, 08:23 PM
Hello,

First post for me. I'm completely clueless when it comes to cars. I have a 2002 Cadillac Deville and the P0171 and P0174 are the error codes.

A month prior my car wouldn't start so I had it towed to the closest shop to my house. Since I just moved to Florida 4 months ago I didn't know any good (or bad) mechanics, so just took it to the closest one. It was a mom and pop garage. They ended up putting in a new starter for me, and according to the guy who just looked at my car at TiresPlus he says to get to the Starter they needed to get under what is broken.

What are the chances that the people who put the starter in my car did something that caused this P0171 and P0174 issue to show up a month later? (The car idles rough). The TiresPlus guy said the repair could be pretty expensive, and my best bet was to call the mom and pop shop and complain and try to get them to take responsibility and fix it for free.

Can you guys give me some advice on what I should say on the phone? I literally don't know what to say, since anything car-related is a whole different language. It'd be helpful to have a few things to mention, if you guys on this forum have anything good in mind.

FWIW, the diagnostic report I got back from TiresPlus (after spending $112 to get it, idk wtf they charged me $112 for, I pulled those codes by myself with my 0 car experience in 10minutes a couple days ago...but w/e). There's handwriting on the paperwork that TiresPlus gave back to me and it says "P0171 - System too lean bank 1" and "P0174 0 - System too lean Bank 2). What's that mean? The guy said if it isn't the 'Boot' it might be the gasket which would be expensive. Any clue how much it would cost me if the mom and pop shop doesn't take care of it? If it's the 'boot' it should be cheaper than the gasket, but I don't know what numbers we're talking about.

Sorry for ranting. Really stressed out over this stuff. I appreciate any help you guys can offer.

Thanks,
Jeff

Ranger
02-16-12, 09:33 PM
:welcome:
If you are getting those two DTC's on a 2000+ it is almost a guarantee that the plenum duct (rubber coupler between the TB and the manifold), or "boot" as they called it has a rip in it. It is basically a vacuum leak and will cause the engine to run lean, thus the two DTC's.

Why was the starter replaced? If they replaced the starter to fix those two DTC's you got ripped off or they just did not know what they where doing. Did they rip the plenum duct while replacing the starter? :noidea:

thx4urm0ney
02-16-12, 10:08 PM
:welcome:
If you are getting those two DTC's on a 2000+ it is almost a guarantee that the plenum duct (rubber coupler between the TB and the manifold), or "boot" as they called it has a rip in it. It is basically a vacuum leak and will cause the engine to run lean, thus the two DTC's.
Thanks for your response. That's a glimmer of good news, since the 'boot' would be cheaper than the other thing. Was the rough guess of $300-$400 realistic to repair that? I think that's what the guy at TiresPlus said it would be. Is it likely that a mechanic could of messed with the plenum duct while replacing the start?

Why was the starter replaced? If they replaced the starter to fix those two DTC's you got ripped off or they just did not know what they where doing. Did they rip the plenum duct while replacing the starter? :noidea:
The starter was replaced for an unrelated issue, but prior to the starter needing to be replaced I never had any issues with rough idling. TiresPlus (and I'm starting to believe it too) seems to believe the mom and pop shop screwed up somewhere.

Ranger
02-16-12, 10:39 PM
The plenum is attached to the manifold which has to be removed to replace the starter, so yes, the mechanic would have had to "mess" with it. It is not a big job, but I have no idea what anyone would charge for that job.

The plenums tend to rip over time. I think PCV gases from the crankcase settle in them after shut down and eventually deteriorate the rubber. It is pretty common. Yours being an '02 may have been deteriorated to the point that just moving it caused it to rip or rip more than it already was and the mechanic never noticed it. I doubt you could call it his "fault", but it would have been nice if he caught it and replaced it at that time since it was already apart and would have only added the cost of the part. I'd go talk to them. Maybe they will replace it and forgo the labor or give you a reduced rate if you explain it nicely.

Testing it is simple. Just flex the plenum duct with your finger while spraying Brakleen or such near the bottom of it while idling. Most likely you'll hear the RPM increase.

Submariner409
02-17-12, 11:13 AM
thx4urmOney, Click on my username, open my profile. 2 albums, 6 pages of pictures, many of your intake manifold, parts, gaskets, plenum, notes. A bit of snooping will give you an idea of what's wrong - and you can do the replacement yourself with simple hand tools and a couple of hours. It's not rocket science, and is all explained, with pictures, in the pages of threads in Discussions, Item Specific, Cadillac Tech Tips.

Google "cadillac forums northstar p0171 p0174" or "cadillac forums northstar intake manifold plenum"

Take a look at www.alldatadiy.com and see if the knowledge available might be of help for you.................

Here's a teaser...................