OBD-II · Engine and powertrain (P)
P207F
AdBlue (reductant) quality performance
What it means
The system judges that the AdBlue is not the right quality - for example diluted with water, contaminated or aged - either from a quality sensor or from poor NOx reduction. On vehicles with SCR, a confirmed unresolved fault may trigger reduced performance or a no-restart countdown; follow the displayed warning and the vehicle handbook.
Symptoms
- AdBlue/emissions warning, possibly with a no-start countdown
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | diluted or contaminated AdBlue (water or wrong fluid added) |
| 02 | old AdBlue that has degraded from heat and time |
| 03 | faulty AdBlue quality sensor in the tank module |
| 04 | NOx sensor giving wrong readings |
| 05 | dosing injector blocked (low real dosing looks like poor quality) |
What to check, step by step
- 01Test the fluid with a refractometer (about 32.5% urea is correct).
- 02If poor, drain the tank, flush and refill with fresh AdBlue (ISO 22241).
- 03Check the dosing injector spray and NOx sensors.
- 04Clear codes and let the system relearn; some cars need a guided quality test with a diagnostic tool.
- 05If fluid is correct, complete the OEM checks for dosing, NOx readings, exhaust leaks and SCR conversion. Test the quality sensor and its wiring if fitted; replace a sensor or tank module only when that component is confirmed faulty.