P0121 error

Maintenance/Repairs
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21

Here¹s the throttle body relearn procedure

  1. Start the engine and let it idle in park for 3 minutes. During that
    period the idle may be higher idle than normal.
    1. After 3 minutes, turn the engine off and leave it off for 60- seconds…
    1. Start the engine again and let it idle in park for 3 minutes one more
      time. During these run periods you may see a check engine light. Scan for
      codes and if you get throttle body related codes, clear them.
    1. If the idle speed is still off, drive the vehicle at speeds above
      44-mph and operate several acceleration and deceleration cycles. Then repeat
      step #3 one last time.
      I have been driving the vehicle for a month now with no issues.
22

Congratulations!

I’m glad you were able to successfully use that procedure

Because on many/most newer GM vehicles, the relearn procedure involves using a factory-level scan tool

So you were able to do it all yourself, without having to bring the truck to a shop :+1:

23

Congratulations on a job well done and sincere thanks for posting back. Your feedback will definitely become part of the database of knowledge that gets used to help others.
You have “paid it forward”, so to speak. :yum:

24

Good for you for not giving up and fixing the problem. Best of luck.