Turn on/off switch

In the diagram for rear lamp, the top wires are voltage, the bottom black wire is ground. The brown wire on either side should be tail lamps, goes hot when you turn on the headlamp switch. The other top wire on either should be for turn signal. With everything turned on, is there voltage on that wire?
Because the front works and the rear don't, possible wiring circuit problem? The voltage for turn signals comes from bcm. The bcm knows when you turn on turn signal switch, either side, then the bcm sends voltage to turn signal lamp at the rear and front.

When the turn signals quit working pull up , down , front to back an back to front on the turn signal switch handle . Do they work when doing this ? Pontiac had bad switch . The power for the turn signals goes through the flasher / hazard module . Could be the switch or the module.
The HAZARD LPS fuse in the left hand instrument panel (LH IP) junction block supplies battery positive voltage to the flasher module, which is part of the hazard switch assembly. The TURN LPS fuse in the LH IP junction block supplies ignition positive voltage to the flasher module. The turn signal lamps may only be activated with the ignition switch in the ON position. When the turn signal switch is placed in either the left or right position, current flow is from the flasher module's output to the turn signal switch assembly. The flasher module then sends an on-off voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, all the turn signal lamps will flash including both IPC turn signal indicators.

Hi John I don't know if you have sorted your problem ? But I would check the wiring behind the switch for corrosion or broken wire if that is ok, I would test the switch for continuity you would require a multi meter, to check for voltage on both sides of the switch, failing that you would probably need a new switch,

The hazard switch gets power from the horn fuse which is hot all the time, and from the turn signal fuse which is hot when the key switch is on. The turn signal switch gets power from the hazard switch and both use the same flasher.
So if the turn signals work but the hazard switch does not power the lights, and both fuses have power, I would say the problem is inside the hazard switch.

sounds like you have a bad turn signal switch.

If the third brake light is working than we know the fuse is good and the switch is good. The third brake light bypasses the turn signal switch. If the rear turn signals are working than we also know that the wiring from the switch to the rear bulbs is also good. The brake lights and the turn signals are on the same bulb so the turn signal switch is what determines if the bulb gets power from the brake light switch or from the turn signal flasher. If the switch is bad usually the first thing that stops working is the brake lights.

Typically you can wiggle, jiggle, pull, push on the switch lever with you foot on the brake and get the brake lights to work. Sometimes turning the four way on and off several times will also get the brake lights to work. If this is the case than a new turn signal switch will solve you problem.

If you have any questions let me know!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

I have found a lot of these turn signal switches bad but check fuse 27 if ok This is a tip turn key one and put turn signal switch in the left or right postion, then push and release the 4 way switch at least 10 times if at any time the turn signals start working while the 4 way switch is off the turn signal is bad. What happens is the contacks in the switch pit and buy working the 4 way switch a bunch of times it scraps through the pits. If they do start working change the switch this isn't a fix its just an easy way to pin point a common problem. If that did work here are the complete test.

What year?

Sounds like a turn signal switch. Earlier models would use the same bulb for the brake and turn signal. The turn signal switch will interrupt power to the brake light and route the signal to either the left or right bulb depending on with way you where turning. Usually you can wiggle the turn signal switch and get the brake light to work momentarily when this is the problem.

Newer vehicles use a lighting module that looks for inputs from the turn signal switch and brake pedal switch and then decides where to send power. This module is also know to go bad.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

If the third brake light works and the regular ones don't, it is most likely a bad turn signal (multifunction) switch. The switch is able to kill the brakes lights to run the turn signals, and in rare circumstances does this. I've seen it several times. It could also be wiring, especially near the turn signal switch, but it is usually the switch.

ck the turn signal switch

This is a common GM specific problem. Your turn signal switch contains an elaborate networking device that has to cancel brakelights while running a turn light. Often times the ground within the turn signal switch is lost causing your situation. After investigating such other possibilities as fuses and loose grounds it may become necessary to replace the turn signal switch. Thank you, Dana