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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 B+ to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
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 (Programming and Relearning)for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool BPP Sensor parameter while applying and releasing the brake pedal. The parameter should change between low counts and high counts when changing between the selected states.

• 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 pressing and releasing the brake pedal. The stop lamps should turn ON and OFF when changing between the selected states.

• 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 when changing between the selected states.

• 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 OFF, test for less than 5 ohm between the low reference circuit terminal C and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal A 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. Test for less than 0.3 V between the signal circuit terminal B and ground.

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

5. Test for 4.8-5.2 V between the 5 V reference circuit terminal A and the signal circuit terminal B.

• If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

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

Stop Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate tail lamp.
2. Test for less than 5.0 ohm between the ground circuit terminal listed below and ground:

* With RPO Z88 - terminal D
* Without RPO Z88 - terminal B

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

3. Connect a test lamp between the control circuit terminal listed below and ground:

* With RPO Z88 - terminal E
* Without RPO Z88 - terminal A

4. 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.

5. If all circuits test normal, test or replace the tail lamp.

Center High Mount Stop Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the center high mounted stop lamp.
2. Test for less than 5 ohm between the ground circuit terminal 1 and ground.

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

3. Connect a test lamp between the control circuit terminal 2 and ground.
4. 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.

5. 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.

* Brake Pedal Position Sensor Replacement ()
* High Mount Stop Lamp Replacement Service and Repair
* Tail Lamp Replacement Service and Repair
* Tail Lamp Bulb Replacement Service and Repair
* Control Module References (Programming and Relearning)for BCM replacement, programming and setup

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