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

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.

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 center high mounted stop lamp.
2. Test for less than 1 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 stop lamp control circuit terminal A and ground circuit terminal B.
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 control circuit for a short to voltage.

^ If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.

5. If all circuits test normal, test or replace the center high mounted stop lamp.

Repair Instructions

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

* High Mount Stop Lamp Replacement (Escalade) High Mount Stop Lamp Replacement (Yukon) High Mount Stop Lamp Replacement (Avalanche) High Mount Stop Lamp Replacement (GMC HP2)