Body Control Module: Description and Operation

Multi-Function Unit - Self-Test
The multi-function unit is located at the rear of the in-car fuse box on the 1995 Classic and on all Discoverys. It's purpose is to operate/control a number of vehicle functions and eliminates the need for multiple individual control units.

Input tests:
- Switch ignition "off"
- Press and hold rear defrost switch then switch on ignition (position 2)-release defroster switch (Note: Release the defroster switch within one second of turning on ignition).
- A series of beeps indicates that the MFU is in diagnostic mode.
- Perform input checks by operating the following switches/controls. A correct input is indicated with a two beep tone.
- Windshield defrost (Classic only)
- Rear window defrost
- Open and close doors and tailgate
- Operate parking/headlamps switch
- Wiper switch in intermittent position
- Windshield/headlamps wash switch
- Rear wiper switch
- Drivers seat belt latch
- Rear fog lamp switch ('97 Discovery only)

Output Tests:
With the system still in diagnostic mode, press and release the rear defroster switch again - now the MFU will provide output signals to the components which will then operate
- Rear window defroster and dash indicator lamps
- Interior lamp
- Headlamp wash (not Defender)
- Front and rear wipers
- Chime and seat belt indicator lamps
- Rear fog lamps ('97 Discovery)
- Windshield heater ('95 Classic)