What P0315 means
Manufacturing tolerances of the crankshaft tone wheel distort the speed fluctuations misfire detection relies on, so the engine module learns a correction for each tooth or segment.
How the engine computer detects it
P0315 means these values have not been learned or are invalid. GM checks that the learned tooth angles add up to 360° (deviation above 0.001° sets the code in the first trip) and learns them with a scan tool: brakes held, full throttle in park until fuel cut-off. Ford learns the profile during up to three overrun phases from 60 to 40 mph and sets P0315 when that fails. Until relearned, misfire detection is suspended – at GM above 1,000 rpm – and misfire readiness stays incomplete. The relearn is needed after replacing the engine, engine module, crankshaft, damper or crankshaft sensor.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on (GM; Ford depending on application)
- Driving usually unaffected
- Misfire readiness not set – emissions test fails
Common causes
- Relearn not performed after replacing sensor, crankshaft, damper, engine or engine module Most likely
- Learned values lost through voltage loss (battery disconnected) Possible
- Tone wheel damaged or shifted, crankshaft runout, dirt on the sensor Possible
- Interference in the crankshaft sensor circuit Less likely
- Engine module memory faulty Less likely
How to diagnose P0315
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: crankshaft position sensor, crankshaft tone wheel, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 3
- Ignition system or misfire
- 15
- Specific fault
Questions drivers ask
Can I drive with code P0315?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0315?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.