P0315: Crankshaft Position System Variation Not Learned

What it means

The PCM has not yet learned the crankshaft position variation table required for accurate misfire detection. After flywheel/sensor replacement or PCM relearn, a procedure must be performed (typically deceleration from a defined RPM with closed throttle).

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The powertrain controller uses learned crankshaft position variation data to distinguish normal crankshaft speed changes from misfires. P0315 means that variation data has not been learned or is unavailable, often after related parts or the controller have been serviced, so the misfire monitor may not work as intended.

Common causes

Most likely first.

1. Crankshaft position variation relearn not performed after relevant service
2. Crankshaft position sensor or wiring fault
3. Incorrect or incomplete control module programming

Symptoms

• Check engine light on
• Engine may run roughly or misfire
• Reduced power or hesitation

How to diagnose it

1. Check freeze-frame data and scan for related crankshaft sensor, misfire, or module communication codes before attempting a relearn.
2. Review recent service history for crankshaft, flywheel, or control-module work that may have left the variation learning incomplete.
3. Inspect the crankshaft position sensor connector and wiring for looseness, damage, or contamination.
4. Use a capable scan tool and the vehicle’s service information to check whether the required variation relearn is available and complete it under the specified conditions.
5. If the relearn will not complete, diagnose the crankshaft position signal and verify that module programming matches the vehicle.

Common fixes

• Perform the manufacturer-specified crankshaft position variation relearn after relevant service.
• Repair a loose or damaged crankshaft position sensor connector or wiring.
• Replace a faulty crankshaft position sensor if testing confirms an invalid signal.
• Correct incomplete or incorrect control-module programming using vehicle-specific service information.

Can I keep driving?

A steady check engine light with normal running usually permits a cautious trip for diagnosis, but avoid hard acceleration if the engine misfires or loses power. If the light flashes or the engine runs roughly, stop when safe because an active misfire can damage the catalytic converter.