B3445
DTC B3445 or B3878
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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 that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the right and left stop lamp control circuits, transmission control module (TCM), engine control module (ECM), and center high mounted stop lamp (CHMSL) control circuit.
Conditions for Running the DTC
* Battery voltage must be between 9-16 V.
* Brakes APPLIED.
Conditions for Setting the DTC
DTC B3445 01
The BCM detects a short to voltage on the left stop lamp control circuit.
DTC B3445 02
The BCM detects a short to ground on the left stop lamp control circuit.
DTC B3445 04
The BCM detects an open/high resistance on the left stop lamp control circuit.
DTC B3878 01
The BCM detects a short to voltage on the right stop lamp control circuit.
DTC B3878 02
The BCM detects a short to ground on the right stop lamp control circuit.
DTC B3878 04
The BCM detects an open/high resistance on the right stop lamp control circuit.
Actions Taken When the DTC Sets
The appropriate brake lamp will not illuminate.
Conditions for Clearing the DTC
* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 malfunction-free ignition cycles have occurred.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left (D61)
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E5A tail/stop lamp.
2. Test for less than 5 ohms between the ground circuit terminal 3 and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Connect a test lamp between the control circuit terminal 1 and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the appropriate Brake Lamp ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 body control module.
* X4 left stop lamp
* X5 right stop lamp
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 body control module.
* X4 left stop lamp
* X5 right stop lamp
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the appropriate E5A tail/stop lamp.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Tail Lamp Bulb Replacement Service and Repair
* Control Module References Control Module References for BCM replacement, programming, and setup