SCR efficiency faults
The ECU compares the NOx sensor readings before and after the SCR catalyst. If too little NOx is being removed, it logs an efficiency fault. The cause can be the catalyst itself, but more often it's an incorrect dosing amount, a faulty NOx sensor, poor-quality AdBlue or an exhaust leak.
Our SCR diagnostic process
- Read stored and pending fault codes from engine and SCR modules
- Compare upstream and downstream NOx sensor live data
- Check AdBlue pressure, pump operation and dosing quantity
- Test fluid quality and inspect for crystallisation
- Check wiring, connectors and heater circuits
AdBlue limp mode and fault codes
Some SCR faults put the vehicle into reduced power (limp mode) as well as starting a countdown. Codes in the P20xx and P22xx range — for example P20EE (SCR efficiency), P204F (reductant system performance) and P20E8 (reductant pressure too low) — are common. A code tells us where to look, not which part to replace, so we test before quoting.
Booking
Most customers drive in to our workshop at Padley Farm, Drove Lane, Sleaford (NG34 8JQ). A mobile service is available within roughly 20 miles of Sleaford for an extra charge, and a non-refundable deposit is required for all mobile call-outs.