For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC B3884 00: Center High Mounted Stop Lamp (CHMSL) Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
CHMSL Supply Voltage | B3884 00 | 1 | 2 | --

1. Stop Lamps Inoperative
2. Stop Lamps Always On

### Circuit/System Description

When the brake pedal is applied, the brake pedal switch normally closed contact signal circuit voltage is interrupted to the body control module (BCM). The BCM then applies a voltage to the CHMSL supply voltage circuit to the center high mounted stop lamp (CHMSL).

### Conditions for Running the DTC

• | The ignition is ON.

• | The stop lamps must be commanded ON.

### Conditions for Setting the DTC

The BCM detects a short to ground in the CHMSL supply voltage circuit when the stop lamps are commanded ON.

### Action Taken When the DTC Sets

The CHMSL does not illuminate.

### Conditions for Clearing the DTC

• | The conditions for setting the DTC are no longer present.

• | A history DTC clears after 100 malfunction-free ignition cycles.

• | The BCM receives the clear code command from the scan tool.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Lighting Systems Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

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

### Circuit/System Testing

1. Disconnect the CHMSL and test for internal shorts between all terminals of the CHMSL assembly.

⇒ | If a short between terminals is found, replace the CHMSL.

2. Test the CHMSL supply voltage circuit for a short to ground.

⇒ | If all circuits/connections test normal, replace the BCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | High Mount Stop Lamp Replacement

• | Control Module References for BCM replacement, setup, and programming