What causes "P0171 Fuel Trim System Lean Bank 1" and how do you fix it?!?!?

The car is bone stock, brought it to the dealer today and they read my code, but can't get to it today.... I'll be in next week for a reprogram, but I've been hearing of people having problems with the CEL coming on after the new flash.... I've got the CEL turned on now, what do I need a new flash for??? Just to have it stay on?!?!? LOL

Any ideas are welcome.....

 

Usually, that code is mostly for a mechanical problem, not a tune related problem. I literally JUST dealt with this pain in the *** for a month with my car (2008 G8 GT). I DID manage to fix it. A lot of the time, the reason for this is a vacum leak. Check the intake manifold for cracks and make sure ALL hoses are snug, not dried out or ripped. A simple loose rubber hose can cause this also. I had to pulled off the intake manifold to replace the intake manifold o ring seals, and then changed the front o2 sensors, and the problem was fixed. Since you are only having the problem is bank 1, which is just like me, I'm guessing it's one of those 2 problems. Change the front o2 sensors first and see if that helps. If the o2 sensor heater breaks or goes bad, this can happen. If that doesn't fix it, try changing the intake manifold gasket (O ring seals).

When does it happen? Start up? After driving around for a little bit? If you know anybody with hptuners, let them scan your car, and pay close attention to what the fuel trims are doing on the guage cluster from when you start your car, to driving it around for a little. Bank 1 for me would go WAY lean at start up, then slowly fix itself after a while.

But first try changing the front o2's. Very likely thats the problem, and its the absolute easiest fix and doesn't involve molesting the car

 

Gas cap....or bad gas....or E85 or air leak. Did you do something involving gas recently?

Check the gas cap. If that's okay check if you got E85. If not then likely bad gas. Run it out and try a tank of Chevron.

Reference from a couple years ago:

http://forums.corvetteforum.com/c6-c...and-p0174.html

 

If it was bad gas, he wouldn't have the problem in only bank 1. He would be showing both codes (P0171 and P0174). And if it was the gas cap, the CEL wouldn't be for only a lean bank, there would be an EVAP error as well

 

There's an issue with the CEL coming on.My 08 did it a couple of times.They reflashed it and it's been good since.I think there's a TSB on it.

 

The tech asked me if I changed to a "performance air filter" or changed the software (tune)....

I told him "Mechanically its bone stock, just the way I bought it from here". The CEL just constantly stays on, it doesn't go out after driving a while. I can check the MAF, intake body and "O" rings (thanks for the tip ) but I don't think its that "simple", because why would I get it in bank 1 and not bank 2 also? I guess it's worth a shot to look though, right?...

(PS~ Not the gas or the cap, as I've been through a few tanks and I only put in good stuff)

 

There is a service bulletine concerning a couple DTCs P0171 and P0174. Apparently there was a problem with the radiator shroud. Which resides directly below the air filter, this issue is about fitment and from what I see, if its out of place it disturbs the incoming air to the air filter and this causes the problem. I have seen aftermarket CAIs cause similar problems and I have seen when the filters have fell off which also causes drivability issues because it disturbs the air flow to the MAF, any turbulance causes signal anomolies which can cause drivability issues.

Here is some of the text from the TSB:

#08-06-04-040: Malfunction Indicator Lamp (MIL) -
Check Engine Light On, DTCs P0171 and/or P0174 Set
(Perform Repair As Outlined) - (Aug 13, 2008)
Subject: Malfunction Indicator Lamp (MIL) -- Check Engine Light On,
DTCs P0171 and/or P0174 Set (Perform Repair as Outlined)
Models: 2007-2009 Chevrolet Corvette (Including Z06)
Condition
Some customers may comment that the check engine light is on.
A scan tool may reveal DTCs P0171 and/or P0174 set in history or current. If the air flow to the air intake/air cleaner assembly is disturbed, the DTCs may be induced.
Cause
This condition may be caused by a gap between the upper radiator air baffle and the bumper beam combined with some beam holes. The gap and holes may cause an air flow disturbance to the air intake/air cleaner assembly. Refer to the pictures below for further clarification.
Correction
This is a picture of the upper radiator air baffle with a large gap that needs to be repaired. Repair
the gap in the panel by making sure the retaining clips are properly seated or by installing new retaining clips, P/N 05973400. To access these clips, the vehicle needs to be raised and the three bolts securing the lower radiator air baffle to the bumper beam need to be removed

This is what was wrong on my 07 Z, once they reseated the air filter assemble no more CELs.

Tom

 

Thanks Tom , but......

Where are the pictures?!?!?

 

See tjwong's reply the pdf file is embedded, complete with all the photo's

http://forums.corvetteforum.com/c6-z...r-invoice.html

Tom

 

Printed and will accompany me next week at the dealer.... Thanks

 

Interesting, informative thread.

Just wondering, when you took the car to the dealer originally, did they clear the code? If so, I presume the CEL came back on shortly thereafter?

If they did not clear the code for you... I believe if the "problem" with the car goes away by itself, the CEL will go off on it's own after a certain amount of drive cycles. But maybe you haven't reached that many "cycles" yet. If the dealer did not clear the code for you, I'm thinking you should get a scanner and clear the code... maybe the CEL will then remain off and you need not start digging into your car. Maybe it was just a one-time "blip" in the system.

In the past, whenever I'd get a code on any of my vehicles, I'd always record it, then clear it... then keep driving. In many or most cases, the code would not come back ever again and the car was fine, thus it would have been a waste of time for me to have started attempting to troubleshoot.

But a few times, the CEL would come back on, then I'd clear it again, and if it came on a third time, I'd then take it seriously, troubleshoot and repair the problem.

I guess the point is, make sure there is truly an issue before you spend time and effort trying to troubleshoot and repair. Or it could be an intermittent thing that will happen only once every 8 months, if so, it's also probably not worth ripping things apart. Remember, don't fix what ain't "broke"!

 

I have a code reader and cleared it at least 5 times before I was given this TSB, I didn't mention it to the dealer as I've learned that telling the dealer what is wrong with your car is a bad idea. Let them do their job.

They came to the same conclusion and fixed my car.

Tom

 

They cleared it, but the CEL just stayed on.....

I had the CEL on for two weeks. I do know enough that if the CEL is flashing, then it's a serious problem and needs to be addressed quickly. I'm not going to rip it apart and try to "fix what ain't broke", but I'm not going to ignore it either.

I will let the dealer tell me what they think, before I whip out the TSB. The car is under full warranty and at least the guys at this dealership are "Corvette conscious". I'll find out next week... Till then, I will still drive it.

 

I have seen these codes show up with guys at the drag strip on C5's when they'd hit the rev limiter.......

I don't doubt anything I've read above, just giving one more thought (scenario) for the OP.

The rev limiter usually would turn on both bank codes but I have also seen it turn on only one.....

 

Good point.

Ok, well in that case you surely need to address the problem.

 

I'm bringing mine in on Monday.The CEL just came on today.It's actually idling better now then it was before!I put some duct tape on the upper shroud to cover the gap between it and the peice behind it.Wonder if that'll do anything... I'm not concerned about the light itself, it's just ugly looking at it while it's on!