so ive had this problem ever since I got the truck. cant really figure it out with out a tester of some sort. I changed the bulbs and still got nothing but when I hook a trailer up to the truck I got reverse lights on the trailer but not the truck. the prevous owner changed the tow wireing so instead of the round plug there the regular normal plug on it instead I ran all the wire back and everything an its all secured no loose ends or any of that and I checked the fuse and that was good. im realy lost on it. ive been driven around now for like 6 months with no reverse lights and pulling in and outa traffic and parking lots suck when ppl don't see your big *** truck moving until your tires are on there hood lol any ideas on what the hell it could be I gave up traceing and trying.

 

well if your getting reverse lights to a trailer, that would indicate the wiring to the trailer plug is getting 12v for the reverse lights thus, meaning all the wiring to that plug is good...

i would be willing to bet that when the PO chanced the tow wiring he either cut the reverse lights wire and forgot to hook it back up or did a half assed job splicing it and it got dirty to the point where it broke the connection. If not that then the ground to the reverse lights got broken some how.

Good Luck, tracing electrical issues are a female dog!

 

I know tell me bout it been trying to figure this out on an off deft with it for a year now kinda use to it realy but do need it fixed I traced the tow wiring and all that looks good like I said I do know it is an aftermarket wiring system do to the big black under the driver tail light and one green wire goes from one light to to the other so I know its not stock I didn't see any dirty or disconnected wires ill have to look again just to really double check cause there might be something I didn't see shoved some where but say its a dirty wire like you said for ex. if I go and cut and respice for a new clean connection wood that fix the dirty wire issue or no. I would like to just rip it all out and start new but I need do to the fact that I tow things at random so my luck as soon as I take it out ill need it

 

Have you checked to make sure there is power to the socket for the bulb? Or have you checked for resistance across the socket? Those have a tendency to go out.

Here is the wiring diagram to check the plug:



CAV CIRCUIT FUNCTION

1L61 16LGLEFT TURN SIGNAL (LG = light green)

2L60 16TNRIGHT TURN SIGNAL (TN = tan)

3L1 18VT/BKBACK-UP LAMP FEED (VT/BK - Violet/Black)

4L7 20BK/YLPARK LAMP RELAY OUTPUT (BK/YL = Black/Yellow)

5L50 16WT/TNBRAKE LAMP SWITCH OUTPUT (WT/TN = White/Tan)

6Z1 18BKGROUND (BK = Black)

 

nah I didn't I don't have a tester but I can prolly borrow one or do the tool rental thing at autozone for one and try that butif that's the case that would make both of them not work but would work on a trailer. only the trailer has reverse lights not the truck