just noticed that my reverse lights have stopped working. for a while now sometimes they would work sometimes they wouldnt (no flickering, just would either turn on or not), but now theyre just kaput. i checked the obvious: fuse and bulbs good, at the plug good ground at the ground pin and 0v at the + pin with the shifter in reverse. you would think maybe its the tranny range sensor or something, but my parking sensors work just fine so unless the parking sensors use a different trigger for some reason i dont think its a signaling issue. is there somewhere where the wiring or something for the reverse lights likes to commonly fail? wiring is 100% stock everywhere as far as i know, even the trailer socket uses the oem harness plug so its more than likely not an issue with custom wiring (again, as far as im aware). any help or ideas appreciated.

 

It helps if you identify what you're working on....

 

I noticed my signature wasn't there when I posted but I figured that maybe it just doesn't show you your own signature for whatever reason, I guess not.
it's a 2004 f150 5.4 non heritage.

okay but now it shows up on this post. weird.

 

Since the PAM works, that eliminates everything upstream (fuse, DTR switch, relay, etc) of the splice that feeds that module.

Schematic is below.

Quick half-split would be to see if you get the reversing lamp power at the 7-pin trailer connector.
If yes, then there's only one connector, C405, between its feed splice S410 and the splice for the two lamps S405.
If no, then there are two upstream connectors to inspect.

C3137 is on the LH frame rail. C411 & C405 are in the rear of the truck behind the bumper. Pull them apart and look for green corrosion in the pin or socket.

 

awesome thanks, ill investigate and let you know how it goes.

 

alright, my lazy *** finally got around to looking into this (cut me some slack, i was working on an expedition and a camaro at the same time, this was the only thing i had that actually ran ).
in a nutshell it turns out it was indeed the 2 mentioned connectors at the bumper, the larger one had a broken clip so it was held in just by the friction of the weather seal. a ziptie took care of that one and after which it passed the wiggle and pull test (with the ENGINE OFF and in reverse with the PARKING BRAKE SET and WHEEL CHOCKS to watch the lights). the smaller one had its clip intact but was simply not fully inserted, so again held in place by the weather seal. snapping it together it also passed the wiggle and pull test, but i was still able to affect the connection by trying to flex the connectors at the seam but only when i was really tugging on them in a way they would never experience in any situation short of getting snagged on a cable/branch/something, so im calling it good enough. i decided to take a look at the connectors on the frame rail just for kicks, but upon pulling the cover off i could tell that they hadnt been touched since they left the factory soon to be 20 years ago. so in lieu of a 100% chance of snapping the clips and retainers i just gave them the wiggle test, which they all passed, so i put the cover back on and declared mission accomplished. also, no corrosion anywhere. a little bit of oxidation, but no corrosion luckily. maybe ill go back and hit them with some deoxit, but meh probably not .
many thanks to projectSHO89 for the info!