Battery voltage for the center high mounted stop lamp (CHMSL) is applied from the CHMSL/DMR/LAMP fuse in the I/P electrical center to the body control module (BCM). When the brake pedal is applied, a signal is applied to the BCM. The BCM then applies a voltage to the CHMSL control circuit to the CHMSL.

The ignition is ON. The stop lamps must be commanded ON.

The BCM receives a ground signal on the CHMSL voltage supply circuit when the stop lamps are being commanded ON.

The CHMSL does not illuminate.

The BCM clears this code from current when the fault is removed from the system.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, press the brake pedal. The CHMSL should illuminate.

1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Verify that a test lamp illuminates between the ground circuit terminal 2 and B+.

⇒	If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.

⇒	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 CHMSL.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.