P0315 – Crankshaft Position System Variation Not Learned means the engine control unit has not completed the required crankshaft position variation (CKP relearn) procedure. Without this calibration, the ECU cannot accurately detect misfires or precisely control ignition timing. This may happen after engine repairs, battery disconnection, PCM replacement, or crankshaft sensor issues. You may notice rough running, misfire codes, or reduced performance. This guide explains what P0315 means, symptoms, causes, diagnosis steps, and the best repair procedures to restore normal engine operation.
What Does P0315 Mean?
P0315 is a generic OBD-II DTC that indicates the ECU has not stored the crankshaft position variation data it needs to correctly monitor combustion events. Most vehicles require a “crankshaft variation relearn” anytime major repairs or sensor replacements occur. Without this calibration, the ECU cannot accurately determine crankshaft speed changes during combustion, and misfire detection may be unreliable.
This code usually appears after replacing the crankshaft position sensor, replacing the PCM, or disconnecting the battery for extended periods, but mechanical faults can also prevent the relearn from completing.
Quick Reference
- OBD-II Family: P-Code (Powertrain)
- Scope: Generic
- System: Crankshaft Position / Ignition Timing
- Difficulty Level: Moderate
- Estimated Repair Cost: €0–€250+
- Last Updated: 7 December 2025
Real-World Example / Field Notes
A sedan received a new crankshaft position sensor after a no-start issue. The engine ran, but P0315 appeared immediately. A crankshaft variation relearn was performed using a bi-directional scan tool, and the code cleared permanently. No parts were needed—only the relearn procedure.
Another vehicle had P0315 due to a weak battery that caused voltage drops during relearn attempts. After installing a new battery and performing the relearn, the ECU successfully stored the crankshaft variation data and misfire monitoring returned to normal.
Symptoms of P0315 – Crankshaft Position System Variation Not Learned
- Check engine light: Usually the main or only noticeable symptom.
- Poor misfire detection: Misfire codes may be inaccurate or inconsistent.
- Slight hesitation: Timing adjustments may be less precise.
- Hard starting: In rare cases if timing calibration is far off.
- Other crankshaft sensor codes: May appear if learning fails repeatedly.
Common Causes of P0315
Most Common Causes
- Crankshaft variation relearn not performed after repairs
- Crankshaft position sensor recently replaced
- PCM replaced, updated, or reprogrammed
- Battery disconnected or voltage dropped during relearn
- Weak battery preventing relearn calibration
Less Common Causes
- Damaged crankshaft position sensor wiring
- Incorrect or low-quality aftermarket CKP sensor
- Excessive crankshaft end play or mechanical timing issues
- Failed PCM unable to store variation data (rare)
Diagnosis: Step-By-Step Guide
Most P0315 repairs involve performing the crankshaft variation relearn using a bi-directional scan tool. If the relearn fails, further diagnosis is needed.
Tools You’ll Need
OBD-II scan tool with relearn capability, multimeter, battery tester, wiring diagrams, and basic hand tools.
- Check freeze-frame data: Confirm P0315 is active and not historical.
- Inspect crankshaft position sensor: Verify connector condition, cleanliness, and correct installation.
- Check battery voltage: Ensure 12.4–12.6V engine off and 13.7–14.7V running.
- Perform CKP variation relearn: Use a scan tool to initiate the procedure following on-screen steps.
- Check for stored CKP/CMP codes: Codes like P0335 or P0340 may prevent a relearn.
- Inspect CKP wiring: Check for corrosion, damaged insulation, or poor connections.
- Verify engine mechanical timing: Misaligned timing chains or belts may prevent successful learning.
- Check reluctor wheel condition: Look for bent, damaged, or missing teeth.
- Test sensor output: Use a multimeter or oscilloscope to check CKP waveform stability.
- Reattempt relearn: After fixing issues, try the CKP relearn again.
Pro Tip: Always perform a crankshaft variation relearn after CKP replacement or PCM programming—even if the engine runs smoothly.
Possible Fixes & Repair Costs
- Perform crankshaft variation relearn: €0–€120
- Replace crankshaft position sensor: €40–€120
- Repair CKP wiring or connectors: €30–€150
- Replace weak battery: €80–€180
- Repair timing-related issues: €200–€600+
- PCM reprogram or replacement: €120–€450+
Can I Still Drive With P0315?
Yes, in most cases the vehicle remains drivable. However, misfire detection may be inaccurate, and engine performance may not be fully optimized. If the engine experiences misfires, stalling, or additional crankshaft/camshaft sensor codes, stop driving until the issue is diagnosed.
Related Codes
- P0399 – Ignition Coil “R” Primary/Secondary Circuit
- P0364 – Reserved
- P0363 – Misfire Detected Fueling Disabled
- P0362 – Ignition Coil “L” Primary/Secondary Circuit
- P0361 – Ignition Coil “K” Primary/Secondary Circuit
- P0360 – Ignition Coil “J” Primary/Secondary Circuit
- P0359 – Ignition Coil “I” Primary/Secondary Circuit
- P0358 – Ignition Coil “H” Primary/Secondary Circuit
- P0357 – Ignition Coil “G” Primary/Secondary Circuit
- P0356 – Ignition Coil “F” Primary/Secondary Circuit
Key Takeaways
- P0315 means the ECU has not completed the crankshaft position variation learning process.
- Most cases require a simple scan-tool relearn procedure.
- Weak batteries, bad sensors, and wiring issues can prevent relearn from completing.
- Proper CKP learning ensures accurate misfire detection and smooth running.
FAQ
Do I always need a relearn after replacing the crankshaft sensor?
Yes. Most vehicles require the crankshaft variation relearn whenever the CKP sensor or PCM has been replaced or reset.
Can I do the CKP relearn without a scan tool?
No. A bi-directional scan tool is required on nearly all vehicles to complete the relearn procedure.
Why does P0315 appear after battery replacement?
Low voltage during startup or ECM reset may erase stored variation data, requiring a relearn.
Will P0315 clear itself after driving?
Rarely. Most vehicles require the relearn procedure to be triggered manually with a scan tool.
Can a bad crankshaft sensor cause P0315?
Yes. If the CKP sensor signal is unstable, the ECU cannot complete the learning process.