Right Brake Light Not Working

[JC1986]

Hey everyone, new member, first post. I have a 2004 Avalanche that I am trying to chase down brake light and cruise control problems on. I have replaced both bulbs with LEDs (problem started before this), the brake light switch, and checked the pigtail for broken wires (found a couple and fixed them). All rear lights work except for the right and third brake light.

I'm at a loss of where to go from here. Any help is greatly appreciated.

 

[ygmn]

Got power at sockets?
If you use LED you need resistor for them to work since computer is looking for s certain amp draw.

 

[JC1986]

Got power at sockets?
If you use LED you need resistor for them to work since computer is looking for s certain amp draw.

I put resistors on the turn signals but not brake/tail lights, had the hyperflash in the turn signals.

The interesting thing to me is that the driver side brake light is working and the passenger side is not. Passenger side tail light, turn signal, and backup lights all work, but the second "filament" does not come on on the passenger side when the brake pedal is pressed. I've swapped bulbs from side to side turned them around, unplugged the pigtail from the junction box.

I know I'm getting some power to the socket because the tail light works.

 

[EXT4ME]

There is a wiring junction up under the right side rear fender that is a well known place for corrosion.

I would give that a good going over.

 

[JC1986]

There is a wiring junction up under the right side rear fender that is a well known place for corrosion.

I would give that a good going over.

I have a new one sitting in my passenger seat I was going to install but when I crawled under there to look at it earlier this week and unplugged the pigtail and all of the contacts to the passenger side seemed fine. Granted, I did not check any of the other terminals. Do you know which plug is the feed? I'm assuming with there being 4 terminals there are three outs and one in.

 

[EXT4ME]

Sorry, no.

I personally have not had to deal with this issue.

Rust and corrosion are not a huge issue in the area I live.

However, this topic has been discussed many times over the years on this forum.

Maybe a deep dive will provide you with the information you seek.

 

[Raekal]

I opened up my service manual real quick and grabbed the external lamp circuits for you. The tail lights are on the second page.

 

[JC1986]

I opened up my service manual real quick and grabbed the external lamp circuits for you. The tail lights are on the second page.

THIS IS AWESOME!!!! I have been looking everywhere for something like this!! Thank you so much!!

So I think my next steps are to check the ground and then maybe the turn signal/flasher module as it seems the white wire coming out of the brake light switch goes there and then to the brake light fuses and on from there as a light blue wire. Please correct me if I'm wrong on this part, I am by no means an electrical expert.

 

[Raekal]

THIS IS AWESOME!!!! I have been looking everywhere for something like this!! Thank you so much!!

So I think my next steps are to check the ground and then maybe the turn signal/flasher module as it seems the white wire coming out of the brake light switch goes there and then to the brake light fuses and on from there as a light blue wire. Please correct me if I'm wrong on this part, I am by no means an electrical expert.

Im not an expert either, but if just go out to your truck and take note of which bulbs in that diagram do and do not work as some share common wiring. You can then test each socket to see if it is receiving power or not (rule out the bulbs) with a multimeter or borrowing a known good bulb. Keep in mind this is a multi platform diagram, so you wont have features like 4 wheel steering and marker lights.

From there, cross out the bulbs that are non functional and trace their leads. Where they intersect with a circuit for another bulb, in this case, the right brake light merges with the other brake light for a signal, you want to make ure there are no breaks. If there are multiple bulbs dead on the same circuit, you can follow the wiring back to find a common fault. The licence plate lights for example share the same brown/ white wire as the tail light for constant power on either side.

But id certainly check all of the fuses and even the fuse connector for continuity as well as the grounding wire before digging too deep like you said. I dont personally know what this junction box looks like, but from my 5 minuite look at this diagram, it would kinda make sense for it being at fault here. Because if it isnt a ground issue,it should be having some functionality shared with the other brake bulb on the opposite side id imagine. Which reinforces what extreme has said about corrosion in that area.