This 2002 GMC Yukon came in with the complaint that the lights on the rear of the truck were working sometimes and sometimes not. The customer had only complained about the turn signals but in testing I found that different lights on both sides were not working properly. I figured it had to be a harness connection of some sort. I started looking around and I found this junction block. When I wiggled the connectors the lights would flicker with the movement. I unplugged the harness connector and water started dripping out and some of the terminals were green.
I installed a new junction block, cleaned and tightened the terminals in the connectors. I added some dielectric grease and put it back together and all of the lights worked. I explained to the customer that the condition could return and if it did harnesses will need to be repaired or replaced. Also in my inspection of the junction block I found a major crack on the back side and after a close inspection I realized the vehicle had been hit in the right rear quarter panel and had only minor damage that had already been fixed but no one thought to look at the junction block or harnesses. This same junction block is used on many of the full sized Chevrolet and GMC trucks from the early 2000’s to at least 2007 Classic series. So if you run into and unusual lighting problem at the rear of any of these trucks you may want to check into this junction block.