After cleaning or replacing the electronic throttle body, disconnecting the battery, or on GM "Engine Power Reduced" faults, an idle/throttle relearn resets the ECU baseline.
Systems involved
- Electronic throttle body
- Idle air control
- PCM
Step-by-step procedure
- Reinstall intake components and ensure no vacuum leaks.
- Connect TOPDON scanner — select Throttle Body Relearn / Idle Relearn / TAC Relearn.
- Turn ignition ON, engine OFF for some procedures; others require warmed engine at idle.
- Follow prompts: may include cycling key, holding pedal, or idling for several minutes.
- Clear P1516, P2101, or P0121 if they were set before relearn.
- Test drive — verify idle is stable and acceleration is normal without limp mode.
Important warnings
- Do not clean throttle body with harsh solvents that damage the coating.
- If relearn fails, check for vacuum leaks and pedal position sensor codes before replacing the throttle body.
Related guides
<a href="/sas-steering-angle-calibration/">Steering Angle Sensor (SAS) Calibration Guide</a> · <a href="/crank-relearn-crankshaft-variation/">Crank Relearn / Crankshaft Variation Learn Procedure</a>
