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
- Inspect the connectors of the NOx sensors (on the exhaust pipe before and after the catalytic converter) and the AdBlue pump: corrosion, water, melted wires near the hot exhaust.
- Check the sensor connector and power supply. NOx sensors often fail from heat and vibration.
- FMI 19 — the sensor isn’t communicating over the CAN bus: check the NOx sensor power fuse and the connector of its module.
- FMI 4 — signal below normal: first the connector and power supply, then the sensor itself.
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
Find the part on Kaspi ShopBefore buying, check the part number or match the part by VIN in the Kaspi “Garage”.
Add the FMI — the second number of the code. It shows what exactly is wrong with the parameter.
Source: Navistar IK1201195: SPN 3216 FMI 4, SPN 1569 FMI 31 (static.nhtsa.gov, MC-10115463)
The explanation comes from the error code reference in the AvtoElektrik PRO app.