EGR Calibration Fault
The ECU detected that the EGR (Exhaust Gas Recirculation) system's calibration data doesn't match actual sensor readings, like a scale that won't zero out properly. This prevents the engine from properly controlling emissions by recirculating exhaust gas back into the combustion chamber.
The ECM monitors EGR valve position feedback and compares it against calibrated baseline values stored in memory. When actual sensor data deviates significantly from expected calibration curves, the fault is triggered. The system uses mass airflow and exhaust temperature data to validate EGR operation.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| EGR Position Sensor Output vs Calibration | Within ±10% of stored calibration values | Greater than ±10% deviation or no correlation detected |
| EGR Flow Estimate Rationality | Matches expected airflow reduction at given load/RPM | Mismatch between commanded and calculated EGR flow |
Code P1308 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, P1308 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.