Could be a break in the wiring or a loose connector somewhere.

 

grunter, which lights in the rear are not working? I would do a visual of all the bulbs and make sure that all of them are working. if they are, then that would lead me to believe it is a computer sensing issue. If you don't have a bulb that is working, let me know which bulb and I will give you some step by step troubleshooting steps to determine where your problem lies and methods for fixing it.

How are you with using a multimeter? If we have to get into the wiring, this is the preferred method of checking the wires.

HOpe to hear from you.

 

Grunter, if it is just a 2 wire bulb base, pull the bulb out and first look at the inside and see if things look good (should be fairly shiny and all silver in there where the bulb makes contact). If it doesn't look good, make sure the lights are off and use a scribe or other sharp object to clean up the contacts to get rid of any rust or other stuff. Try the bulb again and see if things work for you. If not, remove the bulb and then stick a multimeter in where the bulb should go (red lead on one side, black lead on the other). With the lights on, does the multimeter jump to either +12 VDC or -12 VDC? If yes, then you have clips on the connector that have been worn away and you can sometimes bend the clips out to make contact again or you will need to wire up a new bulb base. If you are not getting 12 VDC there, go to the back side of the bulb base and see if you can measure the voltage there. If not able to make contact, you will need to cut the bulb base off then measure the wires there. Do you get 12 VDC now? If yes, bad bulb base, replace. If no, you have a bad wire between the bulb base and where that wire taps off for the other running lights. You will need to replace the wiring between these two points.

Hopefully this gives you a path to follow.