Fuel Composition Pid

[speedracer]

Hello all. I have a 2006 chevy silverado 1500 with flex fuel. I am getting P0172 & P0175 codes. When I check my Fuel Composition Pid it shows a value of 50 ~ 55. I select Reset and it goes back to a normal value and the truck runs fine. This code is occurring more and more and starting to become a nuisance. I wait til i have a 1/4 tank, fill it up then drive at least 10 miles. According to several tech articles I came across, this should stop this from happening but it isn't. Any suggestion on how to stop this value from changing in the future? Thanks!

 

[Marky Dissod]

Since these are pre-cat O2 sensor codes,
1st guess'd be to change the front O2 sensors
2nd guess'd be to change the fuel composition sensor.

Bet that others will chime in with better guesses.

 

[ORVietVet]

Those Z engines are troublesome

 

[stutaeng]

Weird. Codes are lean on bank 1 and rich on bank 2.

I believe when the the alcohol levels get screwed up, it affects both bank the same way, no?

Have you checked for vacuum leaks?

I believe this year has an alcohol content sensor? Not sure how you can test that?

 

[speedracer]

Since these are pre-cat O2 sensor codes,
1st guess'd be to change the front O2 sensors
2nd guess'd be to change the fuel composition sensor.

Bet that others will chime in with better guesses.

Thanks for responding. Another article from way back, that I forgot about suggested the O2 sensors as the voltage
had some bearing in the fuel decision algorithm. There is NO sensor it was replaced by this terrible software decision tree.

 

[speedracer]

Weird. Codes are lean on bank 1 and rich on bank 2.

I believe when the the alcohol levels get screwed up, it affects both bank the same way, no?

Have you checked for vacuum leaks?

I believe this year has an alcohol content sensor? Not sure how you can test that?

Thanks for responding. I was INCORRECT as i quoted a P0171 it was P0172 which is fuel rich. There is no
sensor on this series it is determined by a Rube Goldberg algorithm. How nice an simple it would have been to just
place a toggle switch on the engine ECM - Left E10 Right E85. Could be changed on the fly depending on which gas
was available where you happened to be. Logical and easy = Can't be done!

 

[stutaeng]

Ok, that's correct. I guess I was confusing the alcohol content senser on the GMT900?

Do you ever run that flex fuel in your truck? If not, I'm pretty sure you can simply get rid of it on the ECU tune. Then it will run like a regular non-flex fuel engine.