Code P0174 "System Too Lean"

[CNC]

Sharing information here. My check engine light kept coming on. Code P0174 "System Too Lean". I searched everywhere and tested everything. There were no vacuum leaks. None! The mass air sensor tested good. O2 sensors (4 ea.) all tested good. Gas cap tested good. Usually what causes a 'too lean code' is often, but not always, a vacuum leak. Outside air invading the fuel mixture somewhere. In short, I had ruled out every possible mechanical thing I could find that would set this code? To no avail. It kept coming on.

Finally took it to my Cadillac Dealer. They hooked up their Tech II Code Reader to The ECM. Found that the original XLR Settings had never been "re-flashed' (re-set) and their was a Service Bulletin on it at the dealership. They re-set The ECM using their Tech II and no more P0174 Code and no more check engine light on. Yea! Cost? $168.00. --- FYI, they also checked everything I had previously checked, and like me, found no issues with those items.

 

[stund33]

Great post! I’ve been on the same hunt looking for a vacuum leak. I have P0171 and P0174. The read out from Advanced Auto said the ECM needed to be flashed to new specs. I couldn’t believe it because everyone says these codes are vacuum related. Can’t avoid the dealer on this one. Thanks again!

 

[RDwilkerson]

I (thought) I had found what was causing mine; removed all ducting from the filter to the throttle body, replaced filters, MAF, MAP, and if like mine the air diffuser (some anamal had crushed the bottom opening) then finally the throttle body and gasket removed the fuel rail cleaned the injectors and new seals, removed air plenum new gaskets and retorqed the bolts replace the dirty line at rear of plemum, installed new spark plugs. Now spent $$$ at the ACdelcotds site trying to reprogram. Took it to my mechanic tells me I might need a catilyic converter and did not reflash the ecm lets see $500 in parts 4 hours labor still have the codes. After all the expense and time found the problem I had purchased a MAF that was listed that it would fit a 2005 it did not, the 04-05 uses a differnt one smaller in size! Replaced it with a ACdelco and problem went away.

 

[MPRCTCL]

Base 4.6L or V 4.4L?

 

[RDwilkerson]

Base 4.6L or V 4.4L?

Sorry bout that I have a 4.6 base here is what I was writting about located at bottom and the rubber sleeve going to the throttle body worth checking out this connection requires sliding the rubber over the top using something to lift the rubber over that edge

 

[MPRCTCL]

No reason to be sorry, I really only asked for folks who come across it in future searches.

 

[RDwilkerson]

Well took it in today for emission test light stayed off right up to the time I pull into the test bay, replaced everything from air filters to throttle body retested for leaks. Now calling an xlr expert to maybe to the reflash. Boy this really pi** me off!

 

[mickeytee]

Check the intake manifold bolts 10 or 12 of them 10mm easy to check

 

[RDwilkerson]

As mentioned before R&R everything from filters to plenum gaskets seals throttle body took it to Danny at legions still have codes now tells me I "might" need a converter wtf! Can not get it thru emissions temp plate is running out and cannot get extension if my hair isn't gray enough wife's question driving me crazy hope I don't get instutionalized before I can get to use this nightmare. What happened to 4 on the floor high rise mallory ign and dual quads tuned with a timing light. Now the test equpiment (if you can get it to work with the car) is more than the cost of a paint job! even my 77 vette was easyer to work on.

 

[pure zen]

RD,,,, Is Danny telling you about needing new cat converter, or is that some other place?

Next,, I would ask if that is a 'guess' or the real answer to get the car through emissions.
I wouldn't think that Danny would give you a guess,,,as he is so good as a XLR certified tech.

Nobody wants to pay for guesses......that is a waste of money.

If no tech can get it through emissions,,,, if it was me ,,,,, I'd re-register the car in a AZ county
that doesn't require emissions testing. Might need to get a P.O. Box in that county.

 

[RDwilkerson]

RD,,,, Is Danny telling you about needing new cat converter, or is that some other place?

Next,, I would ask if that is a 'guess' or the real answer to get the car through emissions.
I wouldn't think that Danny would give you a guess,,,as he is so good as a XLR certified tech.

Nobody wants to pay for guesses......that is a waste of money.

If no tech can get it through emissions,,,, if it was me ,,,,, I'd re-register the car in a AZ county
that doesn't require emissions testing. Might need to get a P.O. Box in that county.

The words I "think" Danny used, had the car for 2 weeks and a list of known problems and provided me a bill for $500.00 no other information on it. So rather than keep trying to get my tech2 and GM tds system to talk to each other I ordered a new (or rather a reflashed to my Vin) with all the recent programing. Called Cadillac (Colter) dealer and wanted $408.00 so opted for the ecm reprogramed for $180 i'll install it my self. According to the tech2 that code started at 45000 so assume (you know what that means) it is the ecm recalbration problem. Stay tuned kids it's about to get scarry!

 

[pure zen]

Q: " Stay tuned kids it's about to get scarry!"

We are already there with your posted issues,,,,so be sure to keep us updated on progress before you go ballistic

 

[RDwilkerson]

So yesterday I decieded to run the tech2 to see if the trims had changed after I burned 1/4 tank, recorded the information and brough it inside to read. I plugged it in to the inside power and now that will not work! DCtoDC converter quit (utube). Sooo after much debate and the 200 times trying to connect to the acdelco tds ordered a new ecm using my vin that is preprogramed to the latest software might have mentioned that before. Since the tech2 is nonop have spent about have the price of a new clone and ordered a VCX nano with wifi while I wait for the replacement tech2 part.
Looking at the ox sensors thinking of how in the hell to get to them might be the next change out. I really do not know if I want to try that yet. Might take it to midas and have them weld on some new converters the OEM one's are $900+ and my guess another $1000.00 to install. The paper tags will run out at the middle of this month (January) still no emission. Just to insure the work I have done went back pulled the injectors and checked the torque of the plenum. Next going to build a smoke machine to see if there is a leak somewhere else.

 

[justdennis]

Hello RD, Sorry I can't be much help solving your problem. My only experience with fault codes was solved by making sure the wire connections were in tight, problem solved. I think that's more common than most people think, the shop I took it to first told me I needed a new throttle body. It sounds like you are way past that. The reason for my post is I am thinking about purchasing a VCX nano and was wondering if you are happy with yours. I know you have your hands full now but if you get a chance let me know your thoughts.
Thanks and good luck,
Dennis

 

[RDwilkerson]

Hello RD, Sorry I can't be much help solving your problem. My only experience with fault codes was solved by making sure the wire connections were in tight, problem solved. I think that's more common than most people think, the shop I took it to first told me I needed a new throttle body. It sounds like you are way past that. The reason for my post is I am thinking about purchasing a VCX nano and was wondering if you are happy with yours. I know you have your hands full now but if you get a chance let me know your thoughts.
Thanks and good luck,
Dennis

What wire connections were loose? Hell ill try anything at this point!! VCX Nano comes tomarrow Wends bought it from Amazon from what I have read it has some of the same funtions as the tech2 but has limits. I have tried to get to connect my tech2 to the GM tds but it will not communicate with the tech2 bought several ubs to serial connectors even bought a old taptop with a serial port that didn't work except to unload the pcmi card to a earler program and would not talk to the car until I bought another pcmi card. Am hoping the VCX being wifi will.
Then my tech2 clone took a crap (had it for 3 months) and had to order a new dc to dc electrical device and that will not arrive until next month another $30.00. Needing to get these codes resolved as my paper plate are about to expire and will be illegally driving it till I pass inspection. The biggest problem is not car related but wife always bending my ear about the cost bad mouthing my purchase and on and on gees all I wanted was a car that would fit in the garage and a convertable, never bargoned for this.

 

[justdennis]

OK RD, Let's take a step back, help me understand your problem. What code are you getting and when did you first get it. What changed around that time, by that I mean did you drive through a flood, make any changes or have any work done on the engine just before you got the code? The reason I ask is my problem started a few months after getting the car back on the road after removing the SC/intake manifold. Long story short the electrical connector going into the throttle body was not inserted all the way. It would run fine one day than the next time I would start it I would get a fault code and it would barely run. I would clear the code and she would run fine again for a while. It progressively got worse until I couldn't clear it anymore. I went back to the shop that removed the Intake and they tried to blame it on a faulty throttle body, I eventually found the problem myself. Your problem may be something completely unrelated, but it doesn't cost anything to start checking all your connections and wire harnesses, some might be hard to get at but give it your best shot.
If you read some of my past posts you will see I have had my share of frustrations with this little beauty but that being said there's nothing else I would rather have, for now.
Hang in there,
Dennis

 

[RDwilkerson]

OK RD, Let's take a step back, help me understand your problem. What code are you getting and when did you first get it. What changed around that time, by that I mean did you drive through a flood, make any changes or have any work done on the engine just before you got the code? The reason I ask is my problem started a few months after getting the car back on the road after removing the SC/intake manifold. Long story short the electrical connector going into the throttle body was not inserted all the way. It would run fine one day than the next time I would start it I would get a fault code and it would barely run. I would clear the code and she would run fine again for a while. It progressively got worse until I couldn't clear it anymore. I went back to the shop that removed the Intake and they tried to blame it on a faulty throttle body, I eventually found the problem myself. Your problem may be something completely unrelated, but it doesn't cost anything to start checking all your connections and wire harnesses, some might be hard to get at but give it your best shot.
If you read some of my past posts you will see I have had my share of frustrations with this little beauty but that being said there's nothing else I would rather have, for now.
Hang in there,
Dennis

Okay the codes started just after I bought the car (Ebay) guy swore it could pass emissions where he lived did not test, So took it to an XLR expert (top issues) told me to replace the throttle body, another person said retorqe the plenum so started from the front air filters, then the new MAF, new rubber connector, the air diffuser was found damaged and replaced, more rubber, new MAP, new throttle body and gasket, new rubber again next remove all the injectors and ran cleaner through them installed new seals top and botttom, removed the plenum throughly cleaned every thing including the nest I found in the vally. Installed new gakets new dirty line at rear of plenum brake booster hose was fine. Installed new spark plugs and ign pack rubber. Tested fuel pressure and read at 60 psi lbs? and held for ten minutes. Car idle's at 880-890. I have it back at the shop to have the reflash ecm/pcm if nessary (which I think is the problem) then there is the cat's we are going install plug fouler on the down stream to see if that clears the cat's code. I think the name GM stands for "General Maintenance" every day until you unload it. who's idea was it to put so f...in my modules in a high performance car?

 

[justdennis]

The fact that you have not found the problem is certainly not for lack of trying, I can understand your frustration. Sorry but I have more questions than answers. When you said the problem started just after you bought the car does that mean on your way home or a week/month later? You made no changes to the car before the problem started? Is the car running bad, missing, etc. or is it just the check engine light and fault code? If it does miss, can you clear the code, and it runs ok until you get the fault code again? Considering everything you have already done it acts like a faulty oxygen senser or short in a wire harness, bad ground or loose connection.
I know I'm just grabbing at straws but sometimes it helps to talk it out. Believe me, I'm more comfortable with cars from the 60's.

 

[RDwilkerson]

The fact that you have not found the problem is certainly not for lack of trying, I can understand your frustration. Sorry but I have more questions than answers. When you said the problem started just after you bought the car does that mean on your way home or a week/month later? You made no changes to the car before the problem started? Is the car running bad, missing, etc. or is it just the check engine light and fault code? If it does miss, can you clear the code, and it runs ok until you get the fault code again? Considering everything you have already done it acts like a faulty oxygen senser or short in a wire harness, bad ground or loose connection.
I know I'm just grabbing at straws but sometimes it helps to talk it out. Believe me, I'm more comfortable with cars from the 60's.

I bought the car thru Ebay and did not have a chance to drive it had it shipped to me; the first problem was the top no op after a few demostration to friends and neigbors. Took the car for a shake down run and first emission test when the engine light came on that was when I strated to run through all the steps as previously mentioned. It is now back at the shop and having the mechanic install some testing of sensors by using a spark plug oil fouler on the down stream sensors and reflashing the ecm if required. I do not feel it is a grounding problem but everything is on the table at this point.

 

[justdennis]

I have to tap out at this point, you have tried everything I could think of and more. I purchased my car from an auction so I didn't get to test drive it either. I did at least get to look it over but I think I should have looked closer, the previous owner had concealed some problems that ended up costing a lot to correct. Live and learn. Good luck and please post your findings, I'm very curious to hear what you find.