How an AdBlue system works
AdBlue is a urea solution that is injected into the exhaust ahead of the SCR (selective catalytic reduction) catalyst. Inside the catalyst it converts harmful nitrogen oxides (NOx) into nitrogen and water.
The system is made up of a tank, a heater, a level and quality sender, a pump, a dosing injector, the pipework between them, and NOx sensors before and after the catalyst. The engine ECU monitors all of it. If any part reports a problem, the ECU logs a fault and usually starts a countdown towards a no-start.
AdBlue component faults we repair
The most common causes of an AdBlue system fault we see in the workshop are:
- AdBlue pump faults — pressure not building, pump not priming or electrical failure
- AdBlue dosing injector faults — blocked, sticking or crystallised injectors
- AdBlue tank faults — cracked tanks and failed integrated tank modules
- AdBlue tank heater faults — common in cold weather, the fluid freezes at around -11°C
- AdBlue level sensor faults — tank reads empty after a refill or level jumps around
- NOx sensor faults — upstream or downstream sensor out of range or not responding
- SCR wiring faults — chafed looms, corroded connectors and water ingress
- AdBlue crystallisation — white urea deposits blocking lines and injectors
- AdBlue pressure faults and SCR efficiency faults
AdBlue warning light won't go off?
Topping up the tank only clears the warning if the cause was a low level. If the light stays on after a refill, the system has logged a real fault — often a level sensor, heater, pump or NOx sensor. A reset on its own will not fix this; the fault returns. We diagnose first so you only pay to fix what has actually failed.
Repair or software-based options
Depending on the fault, different repair or software-based options may be available. We diagnose the vehicle and advise on the appropriate solution for the specific vehicle, fault and intended use.
Drive in or mobile
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.