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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

All Countries Except Japan, Korea, Taiwan

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 left tail lamp assembly and CHMSL is provided by G402 and ground for the right tail lamp assembly is provided by G403.

Japan, Korea, Taiwan Only

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 voltage to stop lamp relay coil 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 EXP fuse to illuminate the rear stop lamps and trailer stop lamps. Ground for the left tail lamp assembly and CHMSL is provided by G402 and ground for the right tail lamp assembly is provided by G403.

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 Testing

Stop Lamps Malfunction - All Countries Except Japan, Korea, Taiwan
1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the terminals listed below and ground.

* B+ terminal 1
* B+ terminal 3
* B+ terminal 4

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the respective stop lamp circuits for a short to ground.

3. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
4. Verify that a test lamp illuminates between the low reference circuit terminal C and B+.

• If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

5. Disconnect harness connector at the inoperative stop/turn lamp.
6. Test for less than 5 ohms between the ground circuit terminal C and ground.

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

7. Connect a test lamp between the control circuit terminal B and ground.
8. Ignition ON, command the appropriate LR or RR Turn Signal ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded 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.

9. If all circuits test normal, replace the inoperative stop/turn signal bulb or lamp assembly.

Stop Lamps Malfunction - Japan, Korea, Taiwan Only
1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the B+ terminals listed below and ground.

* B+ terminal 1
* B+ terminal 3
* B+ terminal 4

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the respective stop lamp circuits for a short to ground.

3. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
4. Verify that a test lamp illuminates between the low reference circuit terminal C and B+.

• If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

5. Disconnect the STOP LAMP EXP relay from the rear fuse block.
6. Test for less than 5 ohms between the ground circuit terminal 86 and ground.

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

7. Ignition ON, verify a test lamp does not illuminate between the control circuit terminal 30 and ground.

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

8. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.

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

9. Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86.
10. Apply and release the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released.

• 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.

11. Disconnect the harness connector at the inoperative stop lamp.
12. Ignition OFF, test for less than 5 ohms between the ground circuit terminal H and ground.

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

13. Connect a test lamp between the control circuit terminal B and ground.
14. Connect a 3A fused jumper wire between the stop lamp relay B+ circuit terminal 30 and the control circuit terminal 87. The test lamp should illuminate.

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the bulb.

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

High Mounted Stop Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Test for less than 5 ohm between the ground circuit terminal B and ground.

• 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 A and the ground circuit terminal B.
4. Ignition ON, apply and release the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released.

• 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, replace the CHMSL.

Component Test

Relay Test
1. Ignition OFF, disconnect the relay.
2. Test for 70-100 ohms between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 85
* 30 and 86
* 30 and 87
* 85 and 87

• If not the specified value, replace the relay.

4. Install a 10A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

• If greater than the specified range, replace the relay.

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)
* 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 BCM replacement, setup, and programming

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