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Stop Lamps Malfunction

Stop Lamps Malfunction

Diagnostic Instructions
^ Perform the [Diagnostic System Check - Vehicle Diagnostic Information] prior to using this diagnostic procedure. Diagnostic System Check - Vehicle Diagnostic Information
^ Review [Strategy Based Diagnosis] for an overview of the diagnostic approach. Strategy Based Diagnosis
^ [Diagnostic Procedure Instructions - Vehicle Diagnostic Information] provides an overview of each diagnostic category. Diagnostic Procedure Instructions - Vehicle Diagnostic Information

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-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). The stop lamps will not operate unless the ignition is in the ON position. Ground for the left stop/tail lamp assembly is provided by G402 and ground for the right stop/tail lamp assembly is provided by G403.

Diagnostic Aids

NOTE: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to [Exterior Lighting Systems Description and Operation].

Circuit/System Testing

Stop Lamps Circuit Test
1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the following B+ terminals and ground.
^ B+ terminal 1
^ B+ terminal 2
^ 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, reconnect the X4 harness connector.
4. Disconnect the harness connector at the brake pedal position sensor.
5. Verify that a test lamp illuminates between the low reference circuit terminal A 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.

6. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
7. Reconnect the harness connector at the brake pedal position sensor.
8. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 43 and ground.
^ If the test lamp does not illuminate, test the B+ circuit for an open/high resistance or short to ground.

9. Connect a test lamp between the stop lamp relay control circuit terminal 15 and ground.
10. Observe the test lamp while pressing and releasing the brake pedal. The test lamp should turn on and off.
^ 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 an open/high resistance or short to ground. If the circuit tests normal, replace the BCM.

11. Ignition OFF, reconnect the X2 harness connector.
12. Disconnect harness connector at the inoperative stop/turn lamp.
13. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal G and ground.
^ If greater than the specified range, test the ground circuit for an open/high resistance.

14. Connect a test lamp between the supply voltage circuit terminal MIN and ground.
15. Ignition ON, observe the test lamp while pressing and releasing the brake pedal. The test lamp should turn on and off.
^ If the test lamp is always ON, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

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

High Mounted Stop Lamp Circuit Test
1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal 2 and ground.
^ If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the supply voltage circuit terminal 1 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 supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the supply voltage 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.

Repair Instructions
Perform the [Diagnostic Repair Verification - Vehicle Diagnostic Information] after completing the diagnostic procedure. Diagnostic Repair Verification - Vehicle Diagnostic Information
^ [High Mount Stop Lamp Replacement]
^ [Tail Lamp Replacement]
^ [Control Module References] for BCM replacement, setup, and programming Programming and Relearning
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