A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
Possible causes
- Diluted, dirty or wrong reductant (water, fuel, washer fluid)
- Expired or overheated AdBlue
- Faulty quality sensor or rear NOx sensor
- Clogged AdBlue injector or exhaust leak before the NOx sensor
What you can do yourself
- Check the AdBlue with a refractometer (normal is 32.5%), if it deviates — replace it
- Do not replace parts based on one code: diagnose per the manufacturer’s procedure
- Ask about software updates and service campaigns by VIN
Stop and don’t drive on if:
- The Check Engine light is flashing
- The temperature gauge is in the red or the overheating light is on
- The red oil pressure light is on
- Smoke from under the bonnet, a burning or petrol smell
- Strong jerking, knocking from the engine, or the car barely moves
The explanation comes from the error code reference in the AvtoElektrik PRO app.