After replacing the crankshaft position sensor, PCM, or on some GM/Ford models after battery disconnect, the ECU must relearn crankshaft position variation for misfire detection.
Systems involved
- Engine management
- Crankshaft position sensor
- Misfire detection
Step-by-step procedure
- Install all parts correctly and clear stored codes.
- Connect TOPDON scanner and locate Crank Relearn / Case Learn / Variation Learn in service menu.
- Some vehicles require a specific drive cycle; others use stationary relearn with throttle steps.
- Follow manufacturer prompts — often idle for 2 minutes, then hold RPM at specified value.
- Do not shut off ignition until the scanner confirms relearn complete.
- Road test and verify P0315 or crank-related codes do not return.
Important warnings
- Incomplete crank relearn causes false misfire codes and rough running.
- Procedure varies significantly by make — always follow on-screen TOPDON instructions for your VIN.
Related guides
<a href="/oil-reset-service-light/">How to Reset the Oil Service Light with a TOPDON Scanner</a> · <a href="/sas-steering-angle-calibration/">Steering Angle Sensor (SAS) Calibration Guide</a>
