PIP4578A: SES Light Idle Surge And/Or Reduced Engine Power Mode

[WickedMom]

#PIP4578A: SES Light Idle Surge And/Or Reduced Engine Power Mode With DTCs P0068 P0121 P0506 P0507 P1516 P2101 P2119 And/Or P2176 - Clean Throttle Body And Perform Idle Learn Reset - (Feb 9, 2010)

Models: 2007 Buick Rainier
2007-2009 Cadillac CTS-V, Escalade
2008-2009 Chevrolet Colorado
2006-2009 Chevrolet Avalanche, Corvette, Express, Impala, Monte Carlo, Silverado, Suburban, Tahoe, Trail Blazer
2008-2009 GMC Canyon
2006-2009 GMC Envoy, Savana, Sierra, Yukon
2007-2008 Hummer H2
2008-2009 Hummer H3
2007-2008 Pontiac Grand Prix
2008-2009 Pontiac G8
2006-2009 Saab 97x
With a V8 Engine


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
As carbon builds up in the throttle body of a high mileage vehicle, the ECM/PCM learns to compensate by increasing the throttle plate angle.

If enough carbon builds up, an idle surge, deceleration surge, tip-in hesitation, reduced engine power mode, and/or DTCs P0068, P0121, P1516, P2101, P2119, and/or P2176 may be experienced on high mileage vehicles.

If the throttle body is cleaned without performing an "idle learn reset/reset idle learn" with the Tech 2, the ECM/PCM may continue to compensate for previous carbon build up, causing it to return with a similar concern as well as DTCs P0121, P0506, and/or P0507.

In a similar fashion, if the ECM/PCM of a high mileage vehicle is replaced and/or reprogrammed without performing the Throttle/Idle Learn outlined in SI, the ECM/PCM may no longer compensate for existing carbon build up in the throttle body, causing it to return with a similar concern as well as DTCs P0121, P0506, and/or P0507.

Recommendation/Instructions:
If SI diagnosis does not isolate the cause of this concern, inspect the throttle body bore and plate for obvious carbon build up.

If carbon is present, follow the Throttle Body Cleaning Procedure in SI to clean the throttle body.

After ensuring that the throttle body bore and plate are clean, perform an "idle learn reset/reset idle learn" with the Tech 2 and re-evaluate the concern.

Notice: Depending on the vehicle you are working on, the "idle learn reset/reset idle learn" is normally found on the Tech 2 ECM menu for Module Set Up or Special Functions/TAC System.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

[WickedMom]

I have been starting to see this issue with Yukon/Sierra. Seems to be happening with a lot lower mileage than the bulletin seems to expect.

[SRG963]

If carbon is present, follow the Throttle Body Cleaning Procedure in SI to clean the throttle body.

Thanks for posting this.

Can you describe the cleaning procedure? Would removing the battery cables cause the car to relearn, or is the Tech II needed for this?


I don't have any codes and no surges, but would like to do some preventative maintenance. Should I just use seafoam?

[autoroids]

My throttle body was changed at 1700 mi on my 2009 G8 GT. I had P0121, P1516, and
P2101. My car also went into "safe mode" every time I went WOT. The so called safe mode is the stupidist thing I have ever heard of, and I am surprised that GM has not gotted a law suit over this, because it is dangerous. The car won't go over 20mi/hr or whatever the speed, and has no pickup when safe mode is on. Someone will get rear ended one day guaranteed...anyway, my take on the throttle body issues is that GM has a poor design on their t-bodies, or they are sourcing from the cheapest supplier and the quality sucks on it-SHAME!

[WickedMom]

Safe mode is because of the 'fly by wire'. If they computer loses sight or control of your throttle position sensor(s) it will limit your ability to accelerate. Trust me, it is better to have your car not able to go beyond 20mph vs having a stuck WOT.

Just a thought, if your car is in safe/limp mode, DONT DRIVE IT. Have it towed for safety.

[WickedMom]

Thanks for posting this.

Can you describe the cleaning procedure? Would removing the battery cables cause the car to relearn, or is the Tech II needed for this?


I don't have any codes and no surges, but would like to do some preventative maintenance. Should I just use seafoam?

I have never used seafoam. We use chemicals that are through GM for upper intake cleaning fed through a IV style drip. Throttle body cleaner is used with a toothbrush to manually clean the throttle plate itself. If the relearn is needed, a Tech2 is required.

But this is for Yukons and such, I have seen this issue on them. NOT a G8.

[Tjay74]

I personally have always just cleaned the throttle blade/body by hand and then about every 25,000 miles i run seafoam through the gas tank and through the brake booster system as well.

Always worked great for me, but i also have been putting oil catch cans on my lsx vehicles now as well to limit the oil in the intake that causes this issue.