Quoted from Blackjacker:Fixed this exact issue a few weeks ago. Here, it was a couple of cold/cracked solder joints on the pins for connector J5 on the PPB board. (If I put pressure on the connector the lights would come on; take my hand off and they'd go off.) I ended up reflowing every pin on the PPB while I had it out.
The DE GI is super simple to trace. For the backbox GI it's two separate circuits - Brown+White/Brown and Green+White/Green. (One of those pairs is for the upper set of lights, the other for the bottom - I *think* the brown set is for the upper.)
All four of those wires come out of CN8 on the Power Supply board. From there the two striped wires go to pins 1+3 J5 on the PPB, where they run through fuses and then back out of J5 pins 5+7. Those two outputs from J5 and the brown and green solid wires then head up to the Z-connector and onto the backbox. (I had initially thought the Z connector was my problem because when I mucked around with it my lights came back on, but turned out it was just changing the pressure of the wire harness leaning on the J5 PPB connector when I was moving it around.)
Grab your multimeter and start at one end or the other and find where you lose power - should be a straight shot.
Thanks for the help! This is very useful. I noticed as well the flashers are not coming on or the bumper lights. Could these be related to the same connector J5?
I have to admit I am a novice at using the multimeter, I can test fuses, that is about it. What setting should the MM be on and how do I check for power? Thanks again.