Brake lights will not illuminate when brake is pressed. However, the signals work along with evening lamps as well. They do illuminate with the light switch on, but wont get brighter when I hit the brake. I checked the wires from the fuse box through to the tail lights, nothing seems to be cut. Fuse is still good. I tested the fuse with a test light, and there is current. The brake switches spring in and out fine as the brake moves back and forth. They dont seem to get stuck. I replaced 2 of the bulbs in the tail light housings. It turns out that the sockets that needed them were my signal sockets. One of the brake light sockets still needs a new light. Im under the impression that one brake light should still work while the other is out. Oh yeah, the car has been sitting for about five years. Any Ideas?
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when you said neither works are you saying they do not light up at all? is it both sides or just one if you tell us this we can and will help you. Thanks Mike L.
The STOP LP fuse in the rear fuse block supplies battery positive voltage to the normally open stop lamp switch. When the brake pedal is pressed, the stop lamp switch contacts close and battery positive voltage is supplied to the center high mounted stop lamp (CHMSL) and the turn signal/hazard flasher module stop lamp switch signal input. In response to this input the turn signal/hazard flasher module supplies battery positive voltage to the left and right LED tail lamp assemblies. The CHMSL and left tail lamp have ground at G402. The right tail lamp has ground at G401. The stop lamps illuminate when they receive both power and ground.
es battery positive voltage to the left and right LED tail lamp assemblies. The CHMSL and left tail lamp have ground at G402. The right tail lamp has ground at G401. The stop lamps illuminate when they receive both power and ground.
Stop Lamps
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). Ground for the right rear stop lamp and CHMSL is applied at G402. Ground for the left rear stop lamp is applied at G400. The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.
Do you know what DTC'S - diagnostic trouble codes are ?
DTC B3903 02: Stop Lamp Relay Circuit Short to Ground
DTC B3903 05: Stop Lamp Relay Circuit Open or Short to Voltage
DTC C0277 06: Brake Pedal Position Sensor Circuit Short to Ground or Open
DTC C0277 07 : Brake Pedal Position Sensor Circuit Voltage Above Threshold
DTC C0277 09 : Brake Pedal Position Sensor Circuit Rate of Change Above Threshold
DTC C0278 00: Brake Pedal Position Sensor Not Calibrated
DTC C0870 03 : Device Voltage Reference Output 1 Circuit Voltage Below Threshold
DTC C0870 07 : Device Voltage Reference Output 1 Circuit Voltage Above Threshold
Your best bet mite be to take it to a qulaified repair shop .
Stop Lamps
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a 5-volt reference voltage and low reference to the brake pedal position sensor. The position sensor provides an analog voltage signal back to the BCM that will increase as the brake pedal is applied. When the brake is applied, the BCM will then apply battery voltage to the left and right stop/turn signal lamp supply voltage circuits and the center high mounted stop lamp (CHMSL) supply voltage circuit illuminating the stop lamps. At the same time the BCM applies battery voltage through the signal circuit to the transmission control module (TCM) and the engine control module (ECM) indicating that the brakes are applied.
Ground for the stop lamps is supplied as follows:
• G402 provides ground for the left rear stop/tail/turn signal lamps
• G403 provides ground for the right rear stop/tail/turn signal lamps
• G301 provides ground for the CHMSL
The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.
Battery voltage from the LT TRN/SIG and RT TRN/SIG fuses located in the rear fuse block is also used by the body control module (BCM) for stop lamp operation.
Turn Signal Lamps
Battery voltage supplied to the body control module (BCM) from the fuses listed below is used for turn signal and hazard lamp operation.
• LT TRN/SIG fuse for the left turn signals
• CTSY/RF TRN fuse for the right front turn signal
• RR TRN/SIG fuse for the right rear turn signal
When the turn signal switch is place in either the LEFT or RIGHT position, ground from G300 is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) to cycle the appropriate turn signal indicator ON and OFF.
Ground for the turn signal lamps is supplied as follows:
• G104 provides ground for the left and right front turn signal lamps
• G402 provides ground for the left rear stop/tail/turn signal lamps
• G403 provides ground for the right rear stop/tail/turn signal lamps
Do you have a factory scan tool (tech2) ? Your best bet , take it to the dealer .
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
Turn Signal Lamps
The LT T/SIG and RT T/SIG fuses located in the underhood fuse block supplies battery positive voltage to the body control module (BCM) for turn signal and hazard lamp operation. When the turn signal switch is place in either the LEFT or RIGHT position, ground from G202 is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. The BCM also sends a message via GMLAN to the instrument panel cluster (IPC) to cycle the turn signal indicator ON and OFF depending on the position of the turn signal switch.
Ground for the turn signal lamps is supplied as follows:
• G101 provides ground for the left front turn signal lamp
• G100 provides ground for the right front turn signal lamp
• G302 provides ground for the left and right rear turn signal lamps
The LT T/SIG and RT T/SIG fuses located in the underhood fuse block are also used by the body control module (BCM) for stop lamp operation.
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides both, a 5-volt reference voltage and low reference to the brake pedal position sensor. The position sensor provides an analog voltage signal back to the BCM that will increase as the brake pedal is applied. When the brake pedal is applied, the BCM will then apply battery voltage to the left and right stop lamp supply voltage circuits and the center high mounted stop lamp (CHMSL) supply voltage circuit illuminating the stop lamps. At the same time the BCM signals the transmission control module (TCM) and the engine control module (ECM) that the brakes are applied. Ground for all stop lamps is provided at G302.
The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.
Did you check the fuse's. ? Wouldn't think it's a ground because right an left tail lamp Assembly's use same ground ! Did you check for B+ voltage at the bulb. with a volt meter ? Power is supplied by the BCM . Could be the tail lamp assembly
Sounds like maybe a bad turn signal switch. If the brake and turn signal use the same bulb than the turn signal switch will interrupt the brake signal and supply a turn signal to the bulb. Usually you can wiggle the switch while holding the brake pedal down and get them to intermittently work. If that happens than for sure the switch has failed.
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