P0315
Crankshaft Position System Variation Not Learned.
- Generic
- Powertrain
- Generic code
- Low severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 3
- AreaIgnition system or misfire
- 15
- FaultThe specific fault in that area
What it means
P0315 means the engine control unit has not completed, or has lost, the learned correction for small variations in the crankshaft position signal, such as reluctor wheel tooth tolerances. The learned values are normally needed for accurate misfire detection. The code sets when the learn procedure has not been done or the stored values are missing or invalid, usually after a repair, a battery or control unit disconnection, or a software change.
Symptoms
- Engine warning light on
- Misfire codes stored alongside it, or false misfire detection
- Rough idle or uneven running in some cases
- Poor performance or hesitation if the engine runs in a fallback strategy
- Car otherwise drives normally with only the warning light
Possible causes
- Crankshaft variation learn procedure not carried out after a repair such as replacing the crankshaft sensor, flywheel, flexplate, reluctor wheel or engine control unitlikely
- Learned values erased after memory clearing, battery disconnection or a flat batterylikely
- Faulty or poorly fitted crankshaft position sensor, or incorrect air gap, giving a signal the unit cannot learn frompossible
- Damaged wiring or connector fault on the crankshaft sensor circuit causing signal dropoutspossible
- Damaged or contaminated reluctor wheel or trigger teeth, or a loose flywheel or crank pulleypossible
- Learn conditions never met because of other stored faults, a low battery voltage or the wrong driving conditionspossible
- Faulty engine control unit or outdated software that fails to store learned valuesrare
How to diagnose
- Read all stored codes and freeze frame data, noting any misfire, crankshaft or camshaft correlation codes and whether the code is current or pending
- Ask about recent work, battery disconnection or control unit replacement, as this is the most common trigger
- Check battery condition and charging voltage, since low voltage can stop the learn procedure completing
- Inspect the crankshaft sensor wiring, connector and sensor mounting for damage, oil contamination, corrosion or a loose fit
- Inspect the reluctor wheel or trigger teeth if accessible, and check the flywheel or pulley is secure, as the method depends on the engine
- Check live data for stable engine speed and crankshaft signal, and view the waveform with an oscilloscope if signal faults are suspected
- Fix any other stored faults first, then carry out the manufacturer's crankshaft variation learn procedure, which differs by model and engine
- Clear the code and road test, then recheck that the learn status shows complete and the code does not return
How to fix
- Carry out the crankshaft position variation learn procedure to the manufacturer's method for that model and engine
- Repair or replace damaged wiring or connectors on the crankshaft sensor circuit
- Replace a faulty crankshaft sensor and set the correct air gap or fitting, then relearn
- Replace or properly secure a damaged reluctor wheel, flywheel or crank pulley, then relearn
- Recharge or replace a weak battery, then repeat the learn procedure
- Update or correct the control unit software only where an outdated version is a known cause, and relearn afterwards
Can I keep driving?
The car can usually be driven normally while you book it in, as the code often just means the learn has not been done. If misfire symptoms, rough running or flashing warning light appear, reduce driving and have it checked promptly.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.