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Aran, General Motors
Category: Chevy
Satisfied Customers: 635
Experience:  Chevrolet Technician
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2004 Chevy: My brake lights..light bulbs..driver side..head light

Customer Question

My brake lights stopped working on my 2004 Chevy Silverado. I changed the Fues and the light bulbs but they still dont work. I found a wire dangling from behind the driver side head light. It comes out next to another wire of the same diamiter and the second wite goes to the neg battery terminal. The broke wire is the same length as the one that goes to the battery as if it could go there also.?.? Could this be the reason? All other lights on the truck work fine including the break light on the center top of the cab of the truck. The blinkers, running lights, and back up lights all work. Does anyone have any ideas. Can I get a stop light wiring diagram.
Submitted: 6 years ago.
Category: Chevy
Expert:  Aran replied 6 years ago.

ChevTek :

Hello, I'm Aran. I will assist you with your Chevy issue and see to it that you have a positive experience. Your COMPLETE satisfaction is my goal.

I am uploading a diagram to reference starting at the light green highlight, that is the stoplamp switch. If you follow the red arrows the circuit has to be good all the way over the the fuse called VEH CHMSL as the 3rd brake light works.

So the first step is to back step to the fuse called VEH STOP and check that fuse for power with the brake pedal depressed for power. If it has power then jump to the rear of the vehicle at the junction block rear lamps and check connector C1 TERMINAL B for power with the brake pedal depressed.

If you have power there, the issue is after the junction block, I have had a few bad junction blocks. You could further verify the issue by unplugging connectors C1, C2 AND C4 and then using a small jumper wire from C1 TERMINAL B to either C4 TERMINAL A or C2 terminal D and if each corresponding brake light comes on then yes the rear junction block for the lamps is bad on that circuit.

If you do not have power to the rear light junction block then there is an open in that circuit between the rear light junction block and the fuse block on the left side of the dash or the FUSE BLOCK I/P.

Full Size Image

CLICK HERE for the connectors of the rear junction block.

Check this over and let me know what you find.

If you have additional questions or need any clarification please do not hesitate to ask.

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Expert:  Aran replied 6 years ago.
I will be in and out during the day if you reply, it may be a minute but I will get back with you asap. Thanks Aran.
Customer: replied 6 years ago.



Thanks for the assist. It is 1224 in the morning here in Hawaii right now. I will tackle this in the morning and let you know what I find out.

Customer: replied 6 years ago.
Expert:  Aran replied 6 years ago.
You bet, keep me posted. Aran
Expert:  Aran replied 6 years ago.
Just curious if you found your issue?
Thanks Aran
Customer: replied 6 years ago.

Not yet. I am replacing the junction block today. Hopefully that will fix it. I went to a salvage yard this morning a het one and it didn't fix the problem. My wife is going to the dealership right now to get a new one. The dealer parts guy said he thinks it is the blinker switch thing under the air bag. Could that be true?

Expert:  Aran replied 6 years ago.
Hello, thanks for the reply. When we left off, we were going to check the power on the VEH STOP fuse with the brake pedal depressed.

What did you find there?

Give me some details Smile

Also FYI on older trucks the turn signals and stop lamps did go through the turn signal switch, but on the newer trucks they are on a separate circuit. So no it is not the turn signal switch.

Thanks. Aran
Customer: replied 6 years ago.


I put the millimeter on the setting to check for continuity and put one prong on each side of the fuse port. I had continuity when the break was not pressed but when I pushed the break there was nothing. Do I need to check it in a different way?

Expert:  Aran replied 6 years ago.
Thank you for the information, on your multimeter, set it to the DC volt scale. Place one of the leads to ground (usually silver metal is good) and the other lead to the VEH STOP FUSE. It should get power when the brake pedal is pressed.
Aran and 7 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.


I ran a wire from the neg post on the battery for ground and put the red prong from the millimeter to the fuse and have power when the break is pressed.

Expert:  Aran replied 6 years ago.
Thanks for the accept first off, that actually reassures my commitment to you to see the problem through.

So from that fuse, it travels through the firewall into the underhood fuse block and from there back to the rear junction block. Honestly the next easiest point to check it is at the rear junction block.

The connector is blue and we are looking for power with the brake pedal pushed. The wire is light blue, and it is located in terminal B. Here is the connector.graphic
Use the meter the same way, one end grounded and the other on terminal B. Note do not push the lead into the terminal as is will damage it, if you have to use a small wire or a pin so as to still be able to check power and not damage the terminal.

Do you need any clarification on any of this?
Customer: replied 6 years ago.
I put another new junction block on and still nothing. I followed the steps from your last email and found that there was no power to the blue wire as you had described
Expert:  Aran replied 6 years ago.
We have narrowed it down then, not that the problem area is going to jump right out at us but what we have determined is that somewhere it has lost the brake switch power, in between the fuse and the rear junction block.

The next easiest place to get to it is in the under hood junction block. Take the metal bar off that covers the top of the fuse block, there is 4 13mm bolts holding it in. Then remove the top cover and bottom cover of the fuse block. There is tangs on the bottom cover facing the engine side, I put my fingers up under the bottom of the cover and pull the cover out to release it.

Next tip the fuse block up and with the brake pedal depressed check for power on Connector 3 Terminal F4. If there is power there, the open is between there and the rear junction block.

If there is not power there, check for power with the brake pedal depressed on Connector 1 Terminal E7. If there is power there the fuse block is bad, (not likely) if there is no power, then there is an open between that wire and the fuse block inside.

I will upload some diagrams to help, you can get back to me at your convenience, and depending on where we find the issue, sometimes it is cost effective just to run a new wire.

Here is the diagramsgraphicgraphic

If you need additional questions answered just post back here and it will alert me, thanks again for your patience. Aran
Expert:  Aran replied 6 years ago.
CLICK HERE for instructions on how to access the fuse block, it has diagrams.