2002 Chevy Venture tail light circuit board problems

I have a 2002 (not 2001) Chevy Venture and recently replaced the left rear (drivers side) tail light circuit board. I replaced it with a genuine GM part, and when I connected the wire harness to the circuit board and screwed the tail light assembly back in place, everything works properly for say a half hour or so, then I usually get the fast blinking left turn signal (like a bulb is out). Also, both turn signals come on solid when I hit the brake.

A lot of times, if I turn off the ignition and turn it back on, I’ll get the Service Traction System warning and Traction Off lights in the dash. If I take the assembly apart and push down on the wire harness and put it back together, everything works well for a short time again, but it usually reverts back to the above. It seems to be a loose connection and I thought about some kind of loctite to keep everything in place. Someone also casually mentioned a dielectric grease, which sounds like it would be better.

Any thoughts?

I think the new board you purchased may be faulty and has a loose connection somewhere. It may be just a bad solder joint.

Well, it was the second one I purchased. The first one gave the same problem, that’s why I went w/genuine GM. The problem might be w/my wire harness.

Ok, I would have to agree with you. The brake and turn signal circuits are commonly connected usually with the emergency flasher switch. Try cycling that switch a few times to see if that makes any difference.

If the left rear turn signal light isn’t turning on when you notice the fast flash rate of the turn signal then there is a bad connection to that light somewhere on that leg of the circuit.

Well, I guess I need to give more information. When I hit the left turn signal without the brake applied, it works normally. When I touch the brake, it starts flashing fast (but the turn signal works, just at a faster rate). Take your foot off the brake and it goes back to normal flashing frequency.

I mentioned above that I bought an aftermarket part before and when I installed it, I noticed that the wire harness didn’t “click” in like it should. I had to press pretty hard on it to get it to connect. The same problem as above happened then. It would work for a little while, but would revert to the fast frequency (and same behavior w/the brake applied). I sent it back and bought a GM replacement. This time, the wire harness clicked in properly and it seemed to work for a little while, but then (and from then on) it behaved as above. I think I might get some dielectric grease and see if that helps.

Do you have the dual filament type of bulbs in the rear? If so then swap the the left and right side bulbs and see if that changes things.

Dielectric grease is an insulator type of material. It won’t help fix this kind of problem.

I assume that the right side turn signal works ok and doesn’t have a problem, is that correct?

I looked up some service data for your vehicle and it shows that the wiring for the rear lights is a little unusual. It also shows that there is a trailer harness so check the pigtail and make sure that there isn’t any corrosion on the terminals causing this trouble. If that is ok then remove the left rear brake light and then see if the left turn signal works ok when you step on the brake. If it does then the black ground wire for those lights should be checked for a bad connection to ground. Clean the connection and then see if things work ok when you replace the brake light. A bad ground could cause the brake light current to backfeed through other lights. The info shows the grounds from both sides are spliced together at splice S406 and then tied to a common ground point. There may be a bad slice connection if the other side works ok. If you want to prove that out then use a jumper wire tied to ground and connect it to the black wire going to the board. If things work ok the connection at the splice is most likely where the fault is at.

OK, I took both sides apart. I looked at the wire harness on both. Seems like the right side looks very good. But I looked at the left side and underneath where the female holes accept the metal prongs of the circuit board, the plastic is kind of melted a little. The right side has metal showing (maybe the left side isn’t being grounded properly?).

I then experimented. I swapped cirucuit boards. I had to modify by drilling a hole in each to accept the post (I put electricians tape over the previous holes). Tested both w/o installing into the lens assemblies, and both worked properly. But when I put them in the lens and bolted to the car, the left side gave the fast blinking w/left turn signal on. Right side is fine.

I think this points to a problem w/the left side harness, and pretty much says both circuit boards are OK. Now I have to pinpoint the problem (probably a ground problem like you mention above), which might take a little more work. Not sure what you mean about the splice S406. I looked at where the ground wire goes into the harness. I don’t think I could pull it out. Is that connection something I can purchase new, just in case the plug (female) part is bad?

The ground wire splice connection will most likely be made inside the harness somewhere. You would need to have the factory wiring manual to show you where that location is exactly in the harness to repair it. An easy thing to do but not so easy to find without the manual. In place of that you could just add your own ground point to the black wire going to the board. Either cut the existing black wire to the board and add an extra lenght to it so you can terminate the other end to a good chassis ground point or use a wire tap connector and tap on to the black wire with another wire tied to ground. Problem solved.