B3884

DTC B3884

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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/System Description

Battery voltage is applied at all times to the body control module (BCM) from the CHMSL/BCK-UP Fuse located in the underhood fuse block. When the brake pedal is applied and the BCM receives a brake applied signal from the brake pedal position sensor (BPPS). It then applies battery voltage from the CHMSL/BCK-UP fuse through the CHMSL voltage supply 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 BCM will deactivate power to the CHMSL.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Circuit/System Verification

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

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Ignition OFF, test for less than 5.0 ohm of resistance 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 supply voltage circuit terminal A and ground.
4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states.

• 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, test or replace the CHMSL.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* High Mount Stop Lamp Replacement