A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
What you can do yourself
- Check the AdBlue lines from the tank to the pump and from the pump to the dosing module for kinks, cracks or white crystals.
- A clogged AdBlue pump filter or tank intake screen — have it replaced at a repair shop.
- FMI 0 — the pump runs faster than usual but the pressure doesn’t rise: an air leak, a blockage or a leak in the lines.
- FMI 1 — the pressure is too high: the line to the dosing valve is pinched or frozen, or the dosing valve is clogged.
- See an auto electrician: check the pressure and pump with a scanner.
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
Add the FMI — the second number of the code. It shows what exactly is wrong with the parameter.
Source: Detroit DDC-SVC-MAN-0084: SPN 4374 (static.nhtsa.gov, MC-10141899)
The explanation comes from the error code reference in the AvtoElektrik PRO app.