Diagnostic Instructions

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

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	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Brake Lamps	B3445 02	B3445 04	B3445 01	--
Right Brake Lamp	B3878 02	B3878 04	B3878 01	--

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 centre stop lamp control circuits.

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.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, perform the Brake Lamp Command 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 left

•	E42R Tail lamp right

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

•	E42L Tail lamp left harness connector terminal F

•	E42R Tail lamp right harness connector terminal A

⇒	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 left harness connector terminal B

•	E42R Tail lamp right harness connector terminal E

4. Command the Brake Lamp Command 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 (BCM).

⇒	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 (BCM).

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.