GM Service Manual Online
For 1990-2009 cars only

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 B3445 00: Stop Lamp Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

CHMSL Voltage Supply

B3445

1

2

--

1. Stop Lamps Inoperative

2. Stop Lamps Always On

Circuit/System Description

Battery voltage for the center high mounted stop lamp (CHMSL) is applied from the CHMSL/DIMR 15 amp 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 voltage supply circuit to the CHMSL.

Conditions for Running the DTC

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

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

The CHMSL does not illuminate.

Conditions for Clearing the DTC

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

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 assembly. Clear the DTC. Using a test lamp connected to the positive battery terminal, probe the CHMSL voltage supply circuit.
  2. If the test lamp illuminates, test for a short to ground in the CHMSL voltage supply circuit. If all circuits/connections test normal, replace the BCM.
  3. Replace the CHMSL assembly.

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