Does anyone know the factory troubleshooting procedure for inoperative reverse lamps? I have continuity across the switch, 5V at the switch (?? PCM switched?), the fuse is good, 12v at the fuse... but no power at the back of the truck. If there's a relay that switches the lamps, I can't find it.

The truck is an 03 NV5600.

The switch costs $120, so I'd rather not throw parts at it if I can avoid it.

 

The backup lamp switch controls the flow of battery voltage to the backup lamp bulbs through an output on the back-up lamp feed circuit. The switch plunger is mechanically actuated by the gearshift mechanism within the transmission, which will depress the switch plunger and close the switch contacts whenever the reverse gear has been selected. The switch receives battery voltage through a fuse in the Integrated Power Module (IPM) on a fused ignition switch output (run) circuit whenever the ignition switch is in the On position. A take out of the engine wire harness connects the backup lamp switch to the vehicle electrical system. The backup lamp switch and circuits can be tested using conventional diagnostic tools and methods.

 

^^^ yup... just replaced mine. They had it at auto zone. May also be called park safety switch as it controls that function as well.

 

btw... I think it was $36

 

Is that from the 03 FSM? Again, I don't have battery voltage at the switch, I have 5VDC, which leads me to believe this is PCM voltage and not battery voltage.

 

Should be fused 12v (15a) fuse 38 in the IPM under the hood

 

Right.

My question is what happens between that fuse and the lamps at the rear of the truck? A factory wiring diagram would sort this out in a hurry, but unfortunately, I don't have access to them.

 

There's a reverse light switch mounted on the transmission (located on the passenger side). Very common for the this switch to go out. Recently had to replace mine. Bought one from Quad4x4.com for $25.

MikeyB