Crankshaft Position System Variation Not Learned
The Powertrain Control Module (PCM) has not learned the specific variations of the crankshaft position sensor reluctor wheel. This code is set when the required crankshaft position variation learning procedure has not been successfully completed, often after a PCM replacement or engine repair.
While the vehicle may still run, the PCM cannot accurately detect engine misfires until the variation is learned. This should be addressed soon to ensure proper engine management and prevent potential catalytic converter damage from undetected misfires.
Common symptoms
- Illuminated Check Engine Light
- Inability of the PCM to accurately detect engine misfires
- Engine runs rough or hesitates during acceleration
- Flashing Check Engine Light if actual misfires occur but are miscalculated
- Failed vehicle emissions test
Likely causes
- Crankshaft position variation relearn procedure not performed after a PCM or sensor replacement
- Faulty crankshaft position sensor
- Damaged or loose crankshaft reluctor wheel
- Wiring or connector issues in the crankshaft position sensor circuit
- Faulty Powertrain Control Module (PCM) or programming error
What to check before replacing parts
Verify if any recent repairs were made to the PCM, engine, or crankshaft sensor.
Look for: A history of recent component replacement strongly indicates that a simple CASE (Crankshaft Angle Sensor Error) relearn procedure is all that is needed.
Perform the crankshaft position variation relearn procedure using a capable bi-directional scan tool.
Look for: The scan tool should indicate a successful relearn, and the code should clear and not return after a test drive.
Inspect the crankshaft position sensor wiring harness and connectors for damage or corrosion.
Look for: Look for frayed wires, loose pins, or moisture in the connector that could disrupt the sensor signal.
Test the crankshaft position sensor output signal using an oscilloscope.
Look for: A clean, consistent square wave or sine wave (depending on sensor type) without dropouts or erratic spikes indicates a healthy sensor.
Inspect the crankshaft reluctor wheel for physical damage or debris, if accessible.
Look for: Missing teeth, bent teeth, or excessive metal shavings on the wheel can prevent the PCM from learning the variation.
This page explains the generic P0315 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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