Crankshaft Position System Variation Not Learned
Your engine's computer couldn't learn the crankshaft's position variation pattern, like a student unable to memorize a lesson. This usually happens after battery disconnect, ECU replacement, or when the engine can't complete its learning cycle.
The ECU monitors crankshaft position sensor signals to detect engine speed variations and learns normal patterns for that specific engine. It uses this 'learned' variation map to optimize ignition timing and fuel injection. When the learning process doesn't complete, the ECU lacks the baseline data needed for proper engine control.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CMP/CKP Variation Learn Status | Learning complete (bit set) | Learning not complete or failed |
| Crankshaft Position Variation | Within learned tolerance band | Data not available or excessive deviation |
Code P0315 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0315 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.