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 control unit switches the compressor’s air delivery on and off through the governor solenoid valve at the air dryer.
- FMI 3, 4, 5 — an open or short in the solenoid valve circuit: the connector and wires — go to an auto electrician.
- With this fault the compressor often keeps pumping non-stop: the pressure rises above normal, the safety valve pops off and the air dryer cartridge gets wet faster.
- Check the brake circuit pressures on the dashboard: if they’re low or the low air pressure light is on, don’t drive.
- Electrics (sensors, valves, wiring, control unit) — to an auto electrician. Leaks and mechanical faults — to an air brake specialist.
Stop and don’t drive on if:
- The low air pressure light is on or the buzzer sounds
- The air pressure gauges on the dashboard are below the normal range or dropping
- The brakes have got worse, or the vehicle is braking by itself
Add the FMI — the second number of the code. It shows what exactly is wrong with the parameter.
Source: Bendix SD-08-12000, Electronic Air Control (static.nhtsa.gov, MC-11009842)
The explanation comes from the error code reference in the AvtoElektrik PRO app.