P0315: Crankshaft Position System Variation Not Learned
P0315 means the engine computer has not learned, or has lost, the correction values for the crankshaft's tooth pattern, so it cannot use its misfire detection. The car usually drives normally, but the check engine light stays on and the car will fail an emissions test until the relearn is done.
You can keep driving
The data lists no limp mode for this code and says driving is usually unaffected. The engine just cannot detect misfires meanwhile, so a real misfire would go unnoticed by the computer, and the car cannot pass an emissions test.
What it means
The crankshaft has a toothed ring (the tone wheel) that the crankshaft sensor reads to measure engine speed. Small manufacturing differences in that ring distort the speed readings the computer uses to spot misfires, so the engine module learns a correction for each tooth or segment. P0315 is set when those values have not been learned or are invalid. On GM vehicles the module checks that the learned tooth angles add up to 360°, and a deviation above 0.001° sets the code on the first trip. It is learned with a scan tool, with the brakes held and full throttle in park until fuel cut-off. Ford vehicles learn the profile during up to three overrun phases (coasting with the foot off the gas) from 60 to 40 mph, and set P0315 when that fails. Until the values are relearned, misfire detection is suspended (at GM above 1,000 rpm) and the misfire readiness monitor stays incomplete. The relearn is needed after replacing the engine, engine module, crankshaft, damper or crankshaft sensor.
Likely causes
- Relearn not performed after replacing the sensor, crankshaft, damper, engine or engine moduleVery likely
The computer needs fresh tooth values after these parts change, and without a scan tool relearn it has none.
- Learned values lost through voltage loss (battery disconnected)Possible
Losing power can erase the stored values, leaving the module with nothing learned.
- Tone wheel damaged or shifted, crankshaft runout, or dirt on the sensorPossible
A damaged or wobbling ring, or a dirty sensor, gives readings that cannot be learned correctly.
- Interference in the crankshaft sensor circuitLess likely
Electrical noise on the signal can corrupt the readings during the learning process.
- Engine module memory faultLess likely
If the module cannot store the learned values, the code returns after each relearn.
What you may notice
- Check engine light on (GM; Ford depending on application)
- Driving usually unaffected
- Misfire readiness not set, so an emissions test fails
What to check, cheapest first
- 1Think back: was the battery disconnected, or was the crankshaft sensor, damper, crankshaft, engine or engine module replaced recently? That points straight to a missing relearn. · you can do it
- 2Read all stored codes and look for related ones such as P0335, P0336, P0316 or P0313, which would point to a sensor or misfire problem rather than only a missing relearn. · mechanic
- 3Inspect the crankshaft sensor and its connector for dirt, damage and loose fit. · mechanic
- 4Check the sensor wiring for damage and sources of interference. · mechanic
- 5Inspect the tone wheel for damage or shifting and check for crankshaft runout (wobble). · mechanic
- 6Run the crankshaft variation relearn with a scan tool following the procedure for the vehicle, then clear the code and confirm it does not return. · mechanic
Related codes
Frequently asked questions
Can I drive with P0315?+
Yes, usually. The engine normally runs as usual, but misfire detection is off until the relearn is done, so get it done soon.
Can a loose gas cap cause P0315?+
No. The code concerns the crankshaft tooth values. A gas cap affects fuel vapor codes, not this one.
Will P0315 pass an emissions test?+
No. The misfire readiness monitor stays incomplete until the values are relearned, which causes a failure.
How do I clear P0315?+
Clearing the code alone is not enough. The relearn has to be performed with a scan tool, which is why the data marks it as not a DIY job.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10