The MFU has a diagnostic function, if you think theres an issue with it give it a try.
The procedure required is:
1. Close all doors and the tailgate.
NOTE: If the oil pressure switch goes open circuit (engine is started) during the following procedure, the MFU will exit the diagnostic mode immediately.
2. Press and hold the heated rear screen switch and switch on the ignition.
3. Release the heated rear screen switch within 2 seconds and the MFU will beep to indicate that it's in diagnostic mode 1.
4. Press the heated rear screen switch; the MFU will beep twice. In turn, operate each of the following switches, heated front screen, rear fog guard lamps, side lights, headlights, front wiper, and rear wiper. The MFU will beep twice each time a switch is operated.
5. Pressing the heated rear screen again will cause the MFU to enter diagnostic mode 2.
6. The MFU will provide outputs to the following in order given below: Heated rear screen relay energised for 2 seconds Heated front screen energised for 2 seconds Courtesy lights energised for 2 seconds Dim dip relay energised for 2 seconds Rear fog guard lamp energised for 2 seconds Headlamp power wash energised for half a second Front wiper energised for half a second Rear wipe/wash energised for half a second
7. The MFU will then exit the diagnostic mode.