P0315 Crankshaft Position System Variation Not Learned

P0315 indicates the crankshaft position system variation has not been learned. Without a valid variation learn, misfire detection and crankshaft speed interpretation can be less reliable.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not force a crank variation relearn while active crank, cam, timing, or misfire faults are still present.

Symptoms of P0315

Rough idle, shaking, or a stumble under acceleration.
A flashing check-engine light during an active misfire.
Power loss and higher fuel consumption.

Common causes of P0315

Worn spark plugs, ignition coils, or plug wires.
Fuel-delivery problems — injectors, pressure, or a lean/rich mixture.
Vacuum leaks, low compression, or a mechanical fault in that cylinder.

Useful checks before replacing parts

Check crankshaft variation learn status, recent PCM replacement, crankshaft sensor replacement, battery disconnect history, and relearn prerequisites.
Inspect crankshaft position sensor signal quality, tone wheel condition, wiring integrity, grounds, battery voltage, and pending CKP or CMP codes.
Follow the vehicle-specific scan-tool relearn procedure only after related sensor, timing, and voltage problems have been corrected.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.