P0315
Crankshaft Position System Variation Not Learned
When a vehicle powertrain module registers the fault code P0315, it points directly to an internal system malfunction identified as "Crankshaft Position System Variation Not Learned". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
Code P0315 means your vehicle detected a problem with the crankshaft position system variation not learned system. Typical symptoms include check engine light on, no drivability symptoms usually, prevents misfire monitoring. Low severity — the car drives normally, but the fault should be diagnosed and resolved within the next few weeks.
Symptoms
Check engine light on, no drivability symptoms usually, prevents misfire monitoring
Common Causes
- PCM was recently replaced or flashed
- Crankshaft position sensor was replaced
- Engine was replaced
- Software glitch in PCM
How to Fix
- 1 Perform CASE (Crank Angle Sensor Error) relearn with scan tool
- 2 Clear code after relearn procedure
- 3 Check for secure sensor mounting
- 4 Update PCM software
Technical Explanation
Code P0315 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
Low-severity fault — you'll notice check engine light on, no drivability symptoms usually, prevents misfire monitoring but the vehicle remains drivable. The risk of ignoring it long-term is a failed smog test and the possibility that a minor $50 fix becomes more complex over time.
Mechanic's Pro Tip
Module replacement should always be the last resort for P0315 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Scan tool relearn procedure: $50 - $150