FIXED 2012 silverado 4.8l p0121

reocurring p0121 customer replaced the throttle body and code still came back. He has cleared it several times to no avail. When I arrived codes was present and CEL was on no other code was in memory. Vehicle didn't exhibit any other symptoms and frankly ran very well. Looking at the freeze frame data revealed that the tp indicated angle % was different than desired I am assuming that's the issue. One thing I noticed is that the TB idle airflow compensation is at 100%. I decided to do a relearn with my scan tool and it brought the idle airflow comp pid down to 0. But now the vehicle has low idle speed it's less than 500 rpm's. I'm at a loss here. Appreciated any help given.

Please verify 5v ref, signal circuit & powers and grounds at TB

5 volt reference is present and stable as is power and ground.

What about the signal wire? Can you back probe the connector and snap throttle to make sure its sending an increased voltage to the pcm? If it is maybe even back probe the same pin on the pcm to make sure there's no voltage drop on the signal wire. The only other thing I can think of is to check the freeze frame data and see if it says what the throttle position was at the time of the code or other conditions to help recreate it. Also might be a good idea to make sure that the signal wire actaul reading matches the PID on the scan tool.

It's fixed. The throttle body was filthy. Customer stated the throttle body was new so I assumed it was. Cleaned the TB and relearned idle.