Reverse lights don't work after switch replacement, contact cleaning

[nerdtalker]

I noticed a little while ago my reverse lights were not working and with the mirror switch in the right position that the passenger mirror wasn't dropping when in reverse. Fuse B5 checked not blown and the tail light bulbs looked ok, so I figured it was the switch on the transmission (I have a 2002 6MT 996TT). I first cleaned all the contacts on the switch on the transmission, then after that didn't work I replaced the switch since the part is only $20. The old switch tested ok with a DMM after removal, and my situation is unchanged.

 

I guess there's a reverse light relay in the rear compartment where the ECU is. Is that the best next step to check? I thought relays rarely died in these cars.

 

I'm not sure what else to troubleshoot or investigate, other than maybe the wiring harness on the switch which looked a little suspect but nothing major. It looked like one pin had pushed out a bit but I pushed it back into place. Is there somewhere to test the switch wiring inside the cabin and verify that the wiring and switch are working?

[Loren]

Just to be sure, take each rear backup bulb out and test it with an ohm meter.

It is a pretty simple circuit - switch, bulb sockets, bulbs, and connectors.

[nerdtalker]

21 hours ago, Loren said:

Just to be sure, take each rear backup bulb out and test it with an ohm meter.

It is a pretty simple circuit - switch, bulb sockets, bulbs, and connectors.

Yeah I only visually inspected before, I'll double check with a DMM.

[Ahsai]

You may also want to check with key ON engine OFF, whether pin 1 of the backup switch socket (with the connector removed from the switch) gets 12v.