Driver's side brake light issue

#1
Hello Nation,

You have all been helpful in the past for my timing chain repair and I hope I can get some more assistance with a pesky brake light issue. First, it is an '07 Envoy 4.2L with 136K on the engine, running solid after my timing chain/cylinder head repair. As mentioned in the title, the driver's side brake light does not work. Passenger side and high mount stop work just fine. Here is what I have done to this point:
Replaced circuit board
Replaced bulbs
Replaced brake light switch
Removed trailer light plug and cleaned corrosion from prongs (wow, what a pain)
I thought for sure after seeing the amount of corrosion on the plug that would be the issue because it is the large white wire on the plug that leads to the frame, but alas, I was wrong. I probed the sockets on the circuit board with my tester and didn't get a light but blew the stop light fuse. I have checked the wire harness underneath and all connections to reverse lights, trailer plug, brake light connectors and everything looks good. I'm at a loss. Should I pull the trailer plug ground and give it a cleaning? Or just check all of the grounds in the rear of the Envoy on the chassis?
 
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#2
Trailer plug should have no impact on your tail light not working.

Does your turn signal work properly on that side? Reverse light? Running (parking) light? If any or all those work normally, then the ground should be OK.

Check the harness connector that plugs into the brake circuit board. Check for a broken wire there or a corroded connector.
 

freddyboy61

Well-Known Member
#3
If the passenger side brake light works, then the problem is with the wiring from the rear fuse box connector C1 pin B2 (lt blue wire) to the driver's side lamp assembly. As Sparky said, check the connections at and in the taillamp assembly carefully.
 
#4
Does your turn signal work properly on that side? Reverse light? Running (parking) light? If any or all those work normally, then the ground should be OK.
Yes, turn signal, parking lights, reverse lights all work on drivers side. Good to know ground is ok. I pulled the body plug to inspect the wire to see if it was kinked or something.

Check the harness connector that plugs into the brake circuit board. Check for a broken wire there or a corroded connector.
Will do. Couldn't see any corrosion in the plug. There is a lot of length to the wire, it was doubled back and taped as well, so I'm wondering if there could be a break there?

If the passenger side brake light works, then the problem is with the wiring from the rear fuse box connector C1 pin B2 (lt blue wire) to the driver's side lamp assembly. As Sparky said, check the connections at and in the taillamp assembly carefully.
Thanks. There are two blue wires, and honestly they both looked light blue to me! Could have been the lighting conditions. A friend is borrowing the vehicle so I'll have to wait until this weekend to look again.

Removed trailer light plug and cleaned corrosion from prongs
This was a long shot, I have towed trailers and the lights worked no problem.
 

mntegra01

Well-Known Member
#5
When I worked in our shop I have replaced a few pigtails for the circuit board. could be broken wire inside insulation. Probe the wire back from connector about 6 inches or so and check for power on the correct wire.
 

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