Buick Regal: DTC B3445 or B3878

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 Descriptors

DTC B3445 01

Brake Lamps Circuit Short to Battery

DTC B3445 02

Brake Lamps Circuit Short to Ground

DTC B3445 04

Brake Lamps Circuit Open

DTC B3878 01

Right Brake Lamp Circuit Short to Battery

DTC B3878 02

Right Brake Lamp Circuit Short to Ground

DTC B3878 04

Right Brake Lamp Circuit Open

Diagnostic Fault Information

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.

Conditions for Running the DTC

B3445 01, B3878 01, B3445 02, B3878 02, B3445 04 or B3878 04

Brake pedal is applied or the headlamp switch is in park or low beam position.

Conditions for Setting the DTC

B3445 01 or B3878 01

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

B3445 02 or B3878 02

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

B3445 04 or B3878 04

The BCM detects an open control circuit.

Action Taken When the DTC Sets

The appropriate brake lamp is inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, perform the Brake Lamps test. The brake lamps should be ON/OFF.

Circuit/System Testing

1. Ignition OFF, disconnect the appropriate harness connector at the tail lamp listed below:

• E42L Tail Lamp Assembly - Left
• E42R Tail Lamp Assembly - Right

2. Test for less than 5 Ω between the appropriate ground circuit harness connector terminal listed below and ground:

• E42L Tail Lamp Assembly - Left harness connector terminal 4
• E42R Tail Lamp Assembly - Right harness connector terminal 4
• If greater than the specified value, test the appropriate ground circuit for an open/high resistance.

3. Connect a test lamp between the appropriate control circuit harness connector terminal listed below and ground:

• E42L Tail Lamp Assembly - Left harness connector terminal 3
• E42R Tail Lamp Assembly - Right harness connector terminal 3

4. Command the Brake Lamps 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 appropriate control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
• If the test lamp is always OFF, test the appropriate control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

5. If all circuits test normal, test or replace the appropriate tail lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Tail Lamp Replacement (5-Door Hatchback 68) Tail Lamp Replacement (5-Door Wagon 35)

Control Module References for BCM replacement, setup and programming.

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