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
- First, on your own: check the AdBlue level, the AdBlue system fuses and relays, and the connectors of the AdBlue pump and of the dosing valve on the exhaust pipe.
- The AdBlue injector often clogs with crystals. It needs cleaning or replacing.
- FMI 3, 4, 5 — an open or short in the dosing valve circuit: the connector and wires near the exhaust pipe.
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 3361 (static.nhtsa.gov, MC-10124185)
The explanation comes from the error code reference in the AvtoElektrik PRO app.