Have had this problem for a while now on my '91 740 Sedan. The reverse lights will not come on. Does anyone have a wiring diagram for the tail lights? and if I am not getting power to the plug what else could it be?

 

there are 2 places that need to be triggered
the PNP switch in the shifter
reverse switch in the transmission

check your PNP switch, shifter linkage bushings and motor mounts

in my case the motor mounts were very bad and it shifter the engine back far enough that the switch on the transition never engaged and therefore no power at the reverse lights