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 injector connector and the wiring under the valve cover.
- FMI 5 — open circuit, FMI 6 — short, FMI 7 — the injector doesn’t respond (mechanical).
- The engine misfires: it runs rough, shakes and smokes.
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: SAE J1939-71: J-1939 SA/SPN/FMI Descriptions (static.nhtsa.gov, MC-10141869)
OA case from Oleg’s practice
- Bus 2018 The engine is misfiring and has lost power, code SPN 653 — injector control circuit. The cause was a damaged contact in the injector connector. We repinned the connector and cleared the codes — the engine runs smoothly and the power is back. How it went ↗
The explanation comes from the error code reference in the AvtoElektrik PRO app.