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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 STOP fuse in the underhood fuse block supplies battery voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery voltage is supplied to the electronic brake control module (EBCM), powertrain control module (PCM), left and right stop lamps, and the center high mounted stop lamp (CHMSL). The stop and CHMSL lamps are grounded at all times.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
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 EBCM BPP Signal parameter while pressing and releasing the brake pedal. The parameter should change between Applied and Released when changing between the selected states.

• If the parameter does not change between the selected states, refer to Stop Lamp Switch 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 mounted stop lamp while pressing and releasing the brake pedal. The center high mounted 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 Mounted Stop Lamp Malfunction.

Circuit/System Testing

Stop Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the ground circuit terminal 2 and ground.

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

3. Ignition ON, verify the scan tool EBCM BPP signal parameter is Released.

• If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the EBCM.

4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the ground circuit terminal 2. Verify the scan tool EBCM BPP signal parameter is Applied.

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the EBCM.

5. Verify the stop lamps and center high mounted stop lamp are illuminated.

• If not the specified value, test the signal circuit for a short to ground or an open/high resistance.

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

Stop Lamp Malfunction
1. Ignition OFF, disconnect the VSES/STOP relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the VSES/STOP relay.

3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

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

4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Turn the stop lamp switch ON and OFF by applying and releasing 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 ground. If the circuit tests normal, replace the stop lamp switch.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the stop lamp switch.

6. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

7. Ignition OFF, disconnect the harness connector at the appropriate tail/stop lamp.
8. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the tail/stop lamp ground circuit terminal G and ground.

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

9. Connect the harness connector at the tail/stop lamp.
10. Ignition ON, connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the tail/stop lamp is activated.

• If the tail/stop lamp does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the tail/stop lamp.

11. If all circuits test normal, test or replace the VSES/STOP relay.

Center High Mounted Stop Lamp Malfunction
1. Ignition OFF, disconnect the VSES/STOP relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the VSES/STOP relay.

3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

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

4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Turn the stop lamp switch ON and OFF by applying and releasing 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 ground. If the circuit tests normal, replace the stop lamp switch.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the stop lamp switch.

6. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

7. Ignition OFF, disconnect the harness connector at the center high mounted stop lamp.
8. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the tail/stop lamp ground circuit terminal B and ground.

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

9. Connect the harness connector at the center high mounted stop lamp.
10. Ignition ON, connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the center high mounted stop lamp is activated.

• If the center high mounted stop lamp does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the center high mounted stop lamp.

11. If all circuits test normal, test or replace the VSES/STOP relay.

Repair Instructions

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

* Tail Lamp Replacement (Service and Repair)
* Tail Lamp Bulb Replacement (Service and Repair)
* Stop Lamp Switch Replacement (Service and Repair)
* High Mount Stop Lamp Replacement (Service and Repair)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness)) Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for EBCM replacement, setup, and programming

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