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Stop Lamps Malfunction




Stop Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information






Circuit/System Description

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 V 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 voltage to stop lamp relay coil side control circuit, transmission control module (TCM), engine control module (ECM), and center high mounted stop lamp (CHMSL). When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage from the STOP LAMPS fuse to illuminate the rear stop lamps.

Reference Information

Schematic Reference

* Exterior Lights Schematics Exterior Lights Schematics

* Ground Distribution Schematics G100

Connector End View Reference

Component Connector End Views Connector End Views By Name

Description and Operation

Exterior Lighting Systems Description and Operation Exterior Lighting Systems

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool Brake Applied Output Signal parameter while pressing and releasing the brake pedal. The parameter should change between ON and OFF as the brake pedal is applied and released.

• If the parameter does not change between the selected states, refer to the Brake Pedal Position Sensor Malfunction.

2. Observe the left and right stop lamps while applying and releasing the brake pedal. The stop lamps should turn ON and OFF as the brake pedal is applied and released.

• If the left or right stop lamps do not change between the selected states, refer to the Stop Lamp Malfunction.

3. Observe the center high mount stop lamp while pressing and releasing the brake pedal. The center high mount stop lamp should turn ON and OFF as the brake pedal is applied and released.

• If the center high mount stop lamp does not change between the selected states, refer to Center High Mount Stop Lamp Malfunction.

Circuit/System Testing

Brake Pedal Position Sensor Malfunction

1. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.

2. Ignition ON, verify that a test lamp does not illuminate between the low reference circuit terminal 2 and ground.

• If the test lamp illuminates, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.

3. Ignition ON, test for 4.8 V and 5.2 V between the 5 V reference circuit terminal 1 and ground.

• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, replace the brake pedal position sensor.

Stop Lamp Malfunction

1. Ignition OFF, disconnect the harness connector X4 at the BCM.

2. Ignition ON, verify that a test lamp illuminates between the stop lamp B+ circuit terminal 4 and ground.

• If the test lamp does not illuminate, and the STOP LAMPS fuse tests normal, test the B+ circuit for a short to ground or an open/high resistance.

3. Connect the harness connector X4 at the BCM.

4. Ignition OFF, disconnect the harness connector at the appropriate stop lamp.

5. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground:

* Tail/Stop and Turn Signal Lamp - Left and Right - Upper and Lower terminal GRD - with Z75 - E52

* Tail Lamp Circuit Board - Left and Right terminal D - with Z75 + E52 and European

* Tail/Stop Lamp - Left and Right terminal GRD - with X88

* Tail/Stop Lamp - Left terminal C X411 - Z88 with E52

* Tail/Stop Lamp - Left terminal B X411 - Z88 without E52

* Tail/Stop Lamp - Right terminal C X412 - Z88 with E52

* Tail/Stop Lamp - Right terminal B X412 - Z88 without E52

* Tail/Stop Lamp - Left and Right terminal 2 - with HP2

• If greater than the specified range, test the ground circuit for an open/high resistance.

6. Connect a test lamp between the appropriate stop lamp control circuit terminal listed below and ground.

* Tail/Stop and Turn Signal Lamp - Left and Right - Upper and Lower terminal MJR - with Z75 - E52

* Tail Lamp Circuit Board - Left and Right terminal E - with Z75 + E52 and European

* Tail/Stop Lamp - Left and Right terminal MJR - with X88

* Tail/Stop Lamp - Left and Right terminal A - Z88

* Tail/Stop Lamp - Left and Right terminal 1 - with HP2

7. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.

• If the test lamp is always ON, test the control circuit for a short to voltage.

• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.

8. If all circuits test normal, test or replace the stop lamp.

Center High Mounted Stop Lamp Malfunction

1. Ignition OFF, disconnect the harness connector X4 at the BCM.

2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 4 and ground.

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance or short to ground.

3. Reconnect the harness connector X4 at the BCM.

4. Ignition OFF, disconnect the harness connector at the center high mounted stop lamp.

5. Test for less than 5 ohms between the ground circuit terminal B and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

6. Connect a test lamp between the stop lamp control circuit terminal A and ground circuit terminal B.

7. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

8. If all circuits test normal, test or replace the center high mounted stop lamp.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* High Mount Stop Lamp Replacement (Avalanche) Service and RepairHigh Mount Stop Lamp Replacement (Yukon) Service and RepairHigh Mount Stop Lamp Replacement (Escalade) Service and RepairHigh Mount Stop Lamp Replacement (Yukon Two-mode Hybrid) Service and Repair

* Tail Lamp Bulb Replacement (Tahoe, Avalanche) Service and RepairTail Lamp Bulb Replacement (Yukon) Service and RepairTail Lamp Bulb Replacement (Tahoe) Tail Lamp Bulb Replacement (Yukon Two-mode Hybrid) Tail Lamp Bulb Replacement (Cadillac) Service and Repair

* Tail Lamp Replacement (Avalanche) Tail Lamp Replacement (Cadillac) Tail Lamp Replacement (Chevrolet Tahoe Two-Mode Hybrid) Service and RepairTail Lamp Replacement (GMC Yukon Two-Mode Hybrid) Service and RepairTail Lamp Replacement (Tahoe, Yukon) Service and Repair

* Brake Pedal Position Sensor Replacement (Without JF4) Brake Pedal Position Sensor Replacement (Without JF4)Brake Pedal Position Sensor Replacement (With JF4) Brake Pedal Position Sensor Replacement (With JF4)

* Brake Pedal Position Sensor Calibration Brake Pedal Position Sensor Calibration

* Control Module References Control Module References for BCM replacement, setup, and programming

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