High mount brake light not working

Do you know how to test using a DVOM - digital volt ohm meter ? Is there B+ voltage going into the brake light switch ? An coming out when the brake pedal is pressed ? What fuse's ? There is only one fuse for the brake lights !
The BRAKE SW fuse in the RH I/P fuse block supplies battery positive voltage to the normally-open stop lamp switch. When you press the brake pedal the switch contacts close and battery positive voltage is supplied to the left and right stop lamp assemblies and to the center high mounted stop lamp (CHMSL). The left and right stop lamp along with the CHMSL are grounded at G302.
Do you know about the right insturment panel fuse box ?
Stop Lamps Inoperative
Step
Action
Yes
No
Schematic Reference: Exterior Lights Schematics
1
Did you perform the Lighting System Diagnostic System Check?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Lighting Systems
2
Press the brake pedal.
Do all of the stop lamps illuminate?
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 3
3
Are all the stop lamps inoperative?
YES - Go to Step 4
NO - Go to Step 7
4
Inspect the BRK SW fuse.
Is the fuse open?
YES - Go to Step 14
NO - Go to Step 5
5
Disconnect the stop lamp switch.
Using a test lamp connected to ground, probe the battery supply voltage circuit of the stop lamp switch connector.
Does the test lamp illuminate?
YES - Go to Step 6
NO - Go to Step 13
6
Install a fused jumper between the battery supply voltage circuit and the stop lamp switch signal circuit of the stop lamp switch connector.
Do the stop lamps illuminate?
YES - Go to Step 12
NO - Go to Step 17
7
Determine if the center high mounted stop lamp is inoperative or the stop/turn lamps are inoperative.
Are the stop/turn lamps inoperative?
YES - Go to Step 8
NO - Go to Step 9
8
Do the turn lamps operate normally?
YES - Go to Step 17
NO - Go to Turn Signal Lamps and/or Indicators Inoperative
9
Disconnect the center high mounted stop lamp.
Using a test lamp connected to ground, probe the stop lamp switch signal circuit of the center high mounted stop lamp at the harness connector.
Press the brake pedal.
Does the test lamp illuminate?
YES - Go to Step 10
NO - Go to Step 15
10
Using a test lamp, probe between the stop lamp switch signal circuit and the ground circuit of the center high mounted stop lamp with a test lamp.
Press the brake pedal.
Does the test lamp illuminate?
Go to Step 11
Go to Step 16
11
Inspect for poor connections at the harness connector of the center high mounted stop lamp. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 19
12
Inspect for poor connections at the harness connector of the stop lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 18
13
Repair a open or high resistance in the battery supply voltage circuit of the stop lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 20
--
14
Repair a short to ground in one of the following circuits:
• The battery supply voltage circuit of the stop lamp switch
• The stop lamp switch signal circuit of the stop lamp switch
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 20
--
15
Repair a open or high resistance in the stop lamp switch signal circuit of the center high mounted stop lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 20
--
16
Repair an open or high resistance in the ground circuit of the center high mounted stop lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 20
--
17
Repair an open or high resistance in the stop lamp switch signal circuit of the stop lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 20
--
18
Verify the stop lamp switch adjustment. Refer to Stop Lamp Switch Adjustment . If OK, replace the stop lamp switch. Refer to Stop Lamp Switch Replacement .
Did you complete the repair?
Go to Step 20
--
19
Replace the center high mounted stop lamps. Refer to High Mount Stop Lamp Replacement .
Did you complete the repair?
Go to Step 20
--
20
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 2

Do you know what electrical testing is and how to do it ? apparently not ! Do you know what a wiring diagram is and how to read one ? Is there B+ voltage going into the brake light switch ? Test this first with a DVOM - digital volt ohm meter . If there is , with the brake pedal pressed ,is there B+ voltage coming out of the switch ? Find a diagram of the wiring harness connector locations look at every connector the brake light wires are in > Check voltage at each connector till voltage disapears . find the open wire , high resistance , what ever is cause B+ voltage not to be there . Watch videos on youtube for voltage drop testing . Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia How to read a wiring diagram . Buy a repair manual . Sorry dude , but if you want to fix car's , learn how .

Yes , with a volt meter . Find the switch an back probe wires ,testing for voltage in , then press the brake pedal an check for voltage on wire going out . You'll need a wiring diagram so you know which wire is the right one's . You can find free wiring diagrams at http://bbbind.com/free_tsb.html enter vehicle info . year make model an engine size .Under system click on lighting ,then under subsystem click on stop lamp . none of the brake lights work including the high mount stop lights ? A electronic module (smart junction box) controls the lower brake lights . The high mount are controlled directly from brake light switch .

there is a seprate ground that mounts to the frame of your car near the light usualy in trunk in between the rear speakers locate and make shure the conection is good.if that dos not solve it on the pasengers side rear light check bulbs for detereated ends if thay are then replace.this shuold solve you problem

check the lt blue wire at upper lamp,(under trunk lid trim panel) for 12 volts when brake is applied. if no voltage,check same color wire at brake lamp switch for voltage.(by brake pedal).if no voltage replace stop lamp switch asm. if voltage is detected at rear by lamp then replace CHMSL asm.(center high mount stop lamp). this lamp is made of many LED's,if some work and some don't you will need to replace lamp asm. can be repaired by a trained GM tech, possibly. there is no seperate fuse or relay for this lamp,only a stop lamp fuse.

There are TSB's for this issue. I chased this issue for months on mine. Go find the TSB's, there's troubleshooting pointing out the faulty part. It could be, the brake light switch, the hazzard light switch itself, the multi-function switch. I had replaced all of these and still had the problem. Wiring that goes from the brake switch to up near the fender was shorting against the fender. I replaced the pigtail, problem fixed. Best bet to help you, is find the TSB's for this problem.

As for the brake lights push brake pedal down while pushing on and wiggling the hazard switch.If the brake lights come on then replace the multi-function switch.

First let's determine which brake lights are not working. Does the high mounted brake light work? Do both left and right brake light not work? If none of the brake light work, the problem could be the brake light switch at the brake pedal OR fuse #12 in the underhood fuse panel.
If only the bake lights at the corner lamp assembly don't work, check fuse #34 in the rear fuse panel.
The module your are referring to is the circuit board located in each of the corner lamp assemblies, check on website www.compnine.com for the part number of this item. I don't believe this is your problem though.

If bulbs are definetly ok you can look behind trim on the left side in the boot, which covers the space between the boot floor and the window, you are looking for a green/red wire in a connector. this is the power cable which supplies both rear side mounted brake lights. You should check for voltage at this wire when pedal depressed. If no voltage you would need to trace this back to where the wire is joined in the loom as it feeds off the wire which supplies the high mounted brake light and you have stated that this works. Would still double check bulbs first though if you did'nt replace them. Hope this helps.

Hey Paul, it's most likely a wiring problem. There is one wire designated for just the running lights. What type of plug does the truck have? Probably 6 or 7 way (6 or 7 wire). You can check the plug-in at the truck with a multi-meter to see if there's power at that point. If there is, then the problem is somewhere from the trailer plug to the lights on the trailer. If you have a 7 way plug, the center plug is for aux. power (back up lights on what you pull, if equipped). One wire is power to the camper battery for a breakaway switch, one for left turn and stop, one for right turn and stop, a ground wire, one for running lights, and one for trailer brakes. To determine what wire does what, 1st with meter check volts of all wires w/ truck and trailer hooked up, truck running, power wire to battery for breakaway should show voltage if equipped w/ a trickle charge, brake wire will show low voltage, approx. 2 volts, apply brakes and should go up to approx. 12 volts, put on L turn signal, meter should go up and down, as power to blinker pulses on and off, do the same to determine which is the R turn signal (put foot on truck brakes will show voltage to brake lights AND brakes, continue w/ process of elimination to determine which is running lights, and exactly where power is not going.