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
- The sensor measures how much urea is in the AdBlue.
- Check the concentration on the “Sensors” tab: the norm is 31.8–33.2 %.
- Poor-quality or diluted AdBlue has been added. Drain it and fill with proper AdBlue.
- FMI 3, 4 — the quality sensor circuit: connector and wires.
- If this code comes together with SPN 3363 (tank heating), check the heating: after a repair the coolant hoses to the AdBlue tank are sometimes swapped, which also causes a quality fault.
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: Navistar IK0700079: DEF Tank Heater, DEF Quality (static.nhtsa.gov, MC-10162033)
The explanation comes from the error code reference in the AvtoElektrik PRO app.