Engine

P0315 — Crankshaft Position System Variation Not Learned

Severity: medium Drive with care, to a shop

What P0315 means

The engine control module measures the crankshaft position sensor signal against the tone wheel and stores small tooth-to-tooth variations. This learned profile lets it detect misfires accurately. P0315 means that learning has not been completed or has failed.

Symptoms

  • Check Engine light on
  • Rough idle
  • Misfires
  • Reduced fuel economy
  • Hesitation or poor acceleration
  • Stalling
  • Hard starting or no-start (on some models after battery disconnect)

Possible causes

  1. Crankshaft relearn not performed or done incorrectly after a repair
  2. Faulty crankshaft position sensor
  3. Damaged or corroded wiring or connector at the sensor
  4. Timing misalignment, such as a stretched chain or jumped belt
  5. Damaged tone wheel (reluctor ring)
  6. ECM replaced without a relearn
  7. Faulty ECM (uncommon)

How to diagnose

  1. Scan all codes and freeze frame data, noting any misfire or cam/crank sensor codes
  2. Find out what work was done recently: sensor or ECM replacement, timing repair, battery disconnect
  3. Inspect the crank sensor connector and harness for chafing, corrosion and oil contamination
  4. Check sensor power, ground and signal pattern with a scope
  5. Inspect the tone wheel teeth for damage or debris
  6. Verify cam-to-crank timing and check chain or belt condition
  7. Run the manufacturer's crankshaft variation relearn with a scan tool and clear the code
  8. Test drive and confirm the code does not return

Common fixes

  • Perform the crankshaft position relearn with a scan tool
  • Replace the crankshaft position sensor and relearn
  • Repair or replace damaged wiring and connectors
  • Correct timing or replace the chain, belt or tone wheel
  • Reflash or replace the ECM if it is faulty

P0315 on different brands

Ford · manuals
Ford lists P0315:54 for its 2024-2025 gasoline engines as unable to learn profile, which describes the monitor condition rather than a confirmed failed part.

Questions and answers

What does P0315 mean?

The ECM could not learn or calibrate the crankshaft position signal variation. It most often appears after a repair where the relearn was skipped, but a bad sensor or wiring can also cause it.

Can I clear P0315 without a scan tool?

You can erase the code, but it will likely return if the relearn has not been done. The relearn usually requires a scan tool that supports the function.

Do I need a relearn after replacing a crankshaft sensor?

Often yes, especially on vehicles where the ECM stores the tone wheel profile. Follow the manufacturer's procedure for your model.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.