Diagnostic Instructions

DTC Descriptors

DTC B3884 01: Center High Mounted Brake Lamp Circuit Short to Battery

DTC B3884 02: Center High Mounted Brake Lamp Circuit Short to Ground

DTC B3884 04: Center High Mounted Brake Lamp Circuit Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Center High Mounted Brake Lamp	B3884 02	B3884 04	B3884 01	--

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 to the body control module (BCM). The BCM will apply battery voltage to the right, left and center stop lamp control circuits and to the trailer lighting converter if installed in the vehicle.

Conditions for Running the DTC

B3884 01

Brakes are not applied.

B3884 02 or B3884 04

Brakes are applied.

Conditions for Setting the DTC

B3884 01

The BCM detects a short to voltage on the control circuit.

B3884 02

The BCM detects a short to ground on the control circuit.

B3884 04

The BCM detects an open control circuit.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lights Schematics

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, perform the Center Brake Lamp Command test. The center brake lamp should be ON / OFF.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the E6 Center High Mounted Stop Lamp (CHMSL).
2. Test for less than 5 Ω between the E6 Center High Mounted Stop Lamp (CHMSL) ground circuit harness connector 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 E6 Center High Mounted Stop Lamp (CHMSL) control circuit harness connector terminal 2 and ground.
4. Command the Center Brake Lamp Command test 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 K9 Body Control Module (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 K9 Body Control Module (BCM).

5. If all circuits test normal, replace the E6 Center High Mounted Stop Lamp (CHMSL).

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.