The MFU has no bearing on the your hazard/horn issues, but there isn't any reason why you can't put it in its diagnostic test, which is a bit "spooky" but cool to see the stuff happening on there own
Circuit Operation, Multi-Function Unit
The multi-function unit (MFU) is mounted on the rear of the passenger compartment fuse box and has an input to operation of the following:
Heated rear screen
Heated front screen
Courtesy lights
Side and headlights
Rear fog guard lamps
Headlamp power wash
Front wipers
Rear wash/wipe
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Testing.
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.
Press and hold the heated rear screen switch and switch on the ignition.
Release the heated rear screen switch within 2 seconds and the MFU will beep to indicate that it's in diagnostic mode 1.
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.
Pressing the heated rear screen again will cause the MFU to enter diagnostic mode 2.
The MFU will provide outputs to the following in order given below:
Heated rear screen relay energized for 2 seconds
Heated front screen energized for 2 seconds
Courtesy lights energized for 2 seconds
Dim dip relay energized for 2 seconds
Rear fog guard lamp energized for 2 seconds
Headlamp power wash energized for half a second
Front wiper energized for half a second
Rear wipe/wash energized for half a second
The MFU will then exit the diagnostic mode