I have a 92 Toyota pickup ext cab, 4 wheel drive with auto disconnecting differential, it's a v6, I believe 3.0, 5 spd manual. I have had an issue with the backup lights not working for some time, however this recently caused a accident backing out of my drive way. I checked the bulbs and they were fine. I couldn't find a fuse, and I read that it runs off of the gauge fuse, which is still good. I also read that the manuals don't have a relay. So I checked the back up switch on the passenger side of the tranny with the 200 ohm function on my voltmeter. I had a steady reading of 12.4-12.6 when the truck was put into reverse. And no reading when put in neutral, so I assumed that the switch is good, so what would be the next bet? All the wires on the back of the truck by the tail lights look good. And I would rather avoid splicing in new wires if I can help it, tracing wires sounds like a pain as well. The wires going to the switch are red with a white stripe and black with a brown stripe. What is the setup for this? I assume one is power in and the other is power out to tail lights...so which is which? Any help in trouble shooting this problem would be greatly appreciated, thanks. Ps I checked the forums and couldn't find a direct solution or question relating to my issue. I did find some helpful pointers that led me in a good direction but now I am stuck and do not have a manual to assist with this issue. Any manual photos or references would also be appreciated.

 

I think that your black/brown wire is actually black/orange. It is power from the gauge fuse. Red/white leaves the switch and goes to the back-up lights. Obviously you don't have a dead short as you are not blowing the gauge fuse. So you either have a high resistance connection, an open in the red/white or a bad ground connection or an open ground.
I doubt that it is a ground, because Toyota uses a common ground system for all for the lights on the rear and this ground ties to the chassis under the right kick panel, If this were bad none of your rear lights (brake, tail or signal) would be working.
Did you have your meter on ohms as you state above or were you reading DC volts?
12.4-12.6 ohms across a closed switch doesn't sound correct, it should be almost zero 0.01 ohms. If that is the resistance, then the switch is bad, but 12.4-12.6 vdc measured on that switch with the key on sounds right!
Put your voltmeter on DC volts and check the black/orange to ground at the transmission for battery voltage. (a straightened paper clip inserted in the back of the connector at the transmission will allow you check the black/orange for battery voltage and then the red/white. If the black/orange reading is battery voltage and the red/white is not you have a bad switch. If everything checks out, then you have to move on.
There are several connectors from when the red/white leaves the transmission switch to when it gets to the back up lights, but there is one under the passengers seat that is easily accessable. This connector connects the cab harness to the harness that goes through the floor and runs along the frame to the rear. Separate the connectors find the red/white wire on the cab side, put the transmission in reverse with the ignition key in the on (run)position. measure the red/white to ground it should be battery voltage. If not then you have to trace the wiring back toward the transmission, the next connector connects the dash harness to the engine harness and is located under the right kick.
Good Luck!

 

Have you cleaned the sockets the blubs go in.

I have had corroded sockets that looked fine to the eye but did not make electrical contact.

See if you have voltage to the socket .

 

Yeah I tested the power wire and found there was power at 11.4 volts going into the switch and then poked the wire and found 0.08 volts coming out. So it is the backup switch. I was testing on ohms when I took the reading before. I'm going to replace the switch and see if that solves the problem.

 

The contacts were good on the tail lights, no voltage there.