2005 Trailblazer on which the third brake light works, but the 2 'regular' lights don't. Turn signals work ok. Fuse under seat (Vehicle stop) is good, so I assume the switch is bad(?).
Where is the switch (by the brake pedal?) and, more importantly, how to remove it?
STOP LAMP SWITCH REPLACEMENT
Remove the left sound insulator.
Remove the pushrod retainer from the brake pedal pin.
Remove the stop lamp switch and the pushrod from the brake pedal pin.
Disconnect the stop lamp switch electrical connector.
Remove the stop lamp switch from the vehicle.
Install the electrical connector to the stop lamp switch.
Position the stop lamp switch on the pushrod and install the assembly on the brake pedal pin.
Install the pushrod retainer to the brake pedal pin. The retainer will snap into place.
Install the left sound insulator.
Also check the stop light fuse #12, 25 amps, and fuse #34, 15 amps. These fuses may be in the under hood fuse panel. Check your owners manual to be sure.
The STOP fuse in the engine wiring harness junction block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the VEHICLE STOP fuse and the VEHICLE CHMSL fuse. The current flow is now to the stop lamps which are grounded at G401 and G402. The center high mounted stop lamp (CHMSL) is grounded at G401.
For trailer wiring, a separate stop lamp circuit is connected through the GMSF to the trailer wiring harness.
Also check to see if there is voltage to the brake lights at the brake light assemblies. The assemblies have a circuit board in them. It is possible that the voltage gets to the lights but the circuit boards are bad, usually from moisture. Have some one step on the brake and check the dark blue wire on the lights to see if you have voltage. If you do than it will probably be the circuit board. The light will have to be replaced because it is a one piece unit.
Some information listed here is from the Alldata information website.
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