P0171...I hate this code

[GTP Version 2.0]

I have had more trouble with this code than anything else. I tried getting my emissions done today and right before I pull up to the station this code sets off, P0171. I went home and checked for loose vacuum hoses, intake tube, and such and all seem fine. I replaced the O2 sensor about 18 months ago so I'm not thinking it was that. And I also fixed the coolant leak problem from the LIM gaskets. I always run 91 octane, and use Seafoam once a month. I'm not sure what else to do. I am almost positive that I have an air leak because when the car is at an idle at a stop light the tach twitches a little, also I just put in a new Eaton bypass valve and can't achieve full boost (2 bars less than max).

[tblake]

supercharger gasket leak? Have you replaced the supercharger gasket? If so, what brand gasket did you use?

at idle spray carb cleaner at all your vacuum lines and gaskets and listen to see if the idle increases.

[TDWPgtp]

o lord, i had that code and spent a fortune trying to fix it. well first things first as far as the boost goes, make sure the plug for the boost sensor is connected, the shop i took my car to forgot to reconnect it and i had that exact same problem. its right by the bypass valve i believe... and well as far as the p0171 mine ended up being my fuel pump. if i recall correctly p0171 one is lean fuel mixture... if so than thats what my problem was. have the fuel pressure checked, and if thats not it u may wanna look into the injectors. try injector cleaner maybe. also try spraying your engine along vac lines and connections, and any gaskets with brake cleaner while the engine is running. if you notice a change in the RPM (you will hear it) than u have a leak somewhere. i had a very long thread on here somewhere that people posted all possible solutions, i can try to find the link if youd like. good luck

[CrazyHorst]

Couple things...

- check EGR hardware
- check PCV system including valve (make sure it rattles)
- check injector o-rings

The service manual recommends disconnecting the MAF and monitoring fuel pressure (can't recall your repair history if you've ever done those before).

[GTP Version 2.0]

I replaced the SC gasket when I got my ported LIM. I tried the carb cleaner spray and didn't notice any RPM increase. I also replaced my EGR gasket about 9 months ago. I ran some Lucas Fuel injector cleaner but still nothing. AS for the fuel injector o rings. One of them was a little worn, but would that cause a barely noticeable rough idle.

I just removed the garlock gaskets that came with my throttle body spacers. I used Red RTV instead on the SC side of the spacer, and my Easy Performance Reuseable rubber gasket on the other throttle body side. The idle is smoother, but the code is still there.

[GTP Version 2.0]

Oh, and I replaced the PCV about when I fixed the LIM coolant leak.

[GTP Version 2.0]

Does anyone know how many miles I have to travel before the OBDII system is ready to be tested?

[CrazyHorst]

Originally Posted by GTP Version 2.0

Does anyone know how many miles I have to travel before the OBDII system is ready to be tested?

I don't follow this question exactly...are you asking what conditions cause the code to auto-reset or are you asking about the "emission warranty"?

Many of the codes require 40 restarts without further incident before they will auto-reset. Of course you can take matters into your own hands and force a reset with a diagnostic tool connected to the ALDL connector.

[tblake]

I dont think RTV should be used to seal manifold vacuum. Somehow I knew the word "garlock" would come up. I would just throw in a couple GM t-body gaskkets, and if you also have a garlock SC gasket. Might be a good idea to swap that out too.

And to answer your question, Yes, a bad injector o-ring could cause a slight misfire and also a P0171 DTC.

[BNaylor]

What are the current short and long term fuel trim values?

[GTP Version 2.0]

I tossed out the Garlock gaskets and everything seems fine for the moment. What I wanted to know was how many miles I have to travel before the system trip cycle is ready to be tested by emissions. I erased the code and drove 50 miles before I went to get my emissions tested, but they said the vehicle is not ready to be tested. They said if anyone erased a code recently then the system would not be ready until I reached a certain mileage.

As for short and long term fuel trim values I don't have a scanner handy to test them. I doubt the ones to rent at autozone cover that feature.

Oh, and to answer your questions tblake, yeah I replaced the SC gasket (originally garlock from ZZP) to a GM SC gasket. I had the Garlock gasket in for one day before I noticed an air and coolant leak.

[Anthony MPM]

make sure you are checking everything while the engine is at operating temperature in case something is expanding with the heat and also check the exhaust on that bank, an exhaust leak before the O2 sensor will cause that code. I doubt it is the fuel pump, your only getting 1 lean code for bank 1.

[RIP]

Originally Posted by tblake

I dont think RTV should be used to seal manifold vacuum.

Everything I've read says silicone will eventually destroy a cat converter. What is RTV? Nearly all silicone.

I you have a MAF sensor read this: http://www.obd-codes.com/p0171

[BNaylor]

Originally Posted by GTP Version 2.0

What I wanted to know was how many miles I have to travel before the system trip cycle is ready to be tested by emissions. I erased the code and drove 50 miles before I went to get my emissions tested, but they said the vehicle is not ready to be tested. They said if anyone erased a code recently then the system would not be ready until I reached a certain mileage.

To answer your question there is no predetermined mileage where the emissions readiness indicators or flags (I/M) will set meaning the car is ready for emissions testing. There are too many variables to include engine temperature. There are continuous and non continuous monitors. It could take just one drive cycle or many. If certain monitors are not ready then the underlying cause must be found or the I/M status will fail and you will flunk emissions testing.

Try this generic/universal drive cycle procedure:

1) Start engine. Let idle for approximately 2 minutes, 30 seconds with A/C on, if possible.
2) Next accelerate up to 55 mph at half throttle.
3) Hold steady 55 mph for approximately 3 minutes.
4) Decelerate to 20 mph without braking.
5) Accelerate back to 55-60 mph at 3/4 throttle.
6) Hold at steady speed of 66-60 mph for 5 minutes.
7) Decelerate, coast down to stop or lowest speed possible without braking.

Check with odb-ii scanner/scan tool and see if I/M status is ready before emissions testing.

[BNaylor]

Gentleman,

After a brief review of the GM Grand Prix Factory Service Manual to clarify and clear the air here are the parameters to set the P0171 DTC (Fuel Trim System Lean) and trigger the MIL SES/CEL Light. Also, it includes drive cycle or trip info.

The fuel trims both short or long term are abnormal when:

LT fuel trim is greater than + 17%. ST fuel trim greater than + 2%.


The PCM module will monitor and turn on the MIL light during the second consecutive trip in which the respective diagnostic is run and failed.

The PCM will turn off the MIL light during the third consecutive trip in which the diagnostics has run and passed.

Unless cleared with a scan tool history DTCs will clear after 40 consecutive warm-up cycles that have occurred without a malfunction.