why is my service suspension light on and i keep getting a code po121 i replaced my gas cap canister gas pedal and my auto start want work but when the code is gone it works if i take the

Asked by Feb 22, 2015 at 01:06 PM about the 2008 Chevrolet Avalanche

Question type: Maintenance & Repair

when I take the neg cable off it will auto start but after a few mile the code comes back and the auto start will not work   code p0121

1 Answer

725

On my 2009 Avalanche, there was an emissions sensor that went bad. I tried all the things you did, which worked for a while then the check engine light came back on. Before I took it to the garage, I lost power at the transmission - pedal all the way in, RPMs to the red and 40 mph, on a major highway. ... it was ~$800 to fix the sensor & flush transmission fluid. Runs like a champ now. Might be worth having your mechanic take a look. Hopefully it's not as expensive a repair as I had.

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