B3878
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 B3878 02
- Right Brake Lamp Circuit Short to Ground
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
Brake pedal is applied.
Conditions for Setting the DTC
B3445 01
The BCM detects a short to voltage on the left rear brake lamp control circuit.
B3445 02
The BCM detects a short to ground on the left rear brake lamp control circuit.
B3878 02
The BCM detects a short to ground on the right rear brake lamp control circuit.
Action Taken When the DTC Sets
B3445 01
The left rear brake lamp will be continuously illuminated.
B3445 02
The left rear brake lamp will be inoperative.
B3878 02
The right rear brake lamp will be inoperative.
Conditions for Clearing the DTC
* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will be a history DTC.
* A history DTC will clear after 50 ignition cycles.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
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 Verification
1. Ignition ON, observe the function of the E5AA tail/stop lamp-left while commanding the Left Brake Lamp ON and OFF with a scan tool. The E5AA tail/stop lamp-left should turn ON and OFF while changing between the commanded states.
• If the E5AA tail/stop lamp-left is always ON or always OFF, refer to Left Brake Lamp Malfunction.
2. Observe the function of the E5AB tail/stop lamp-right while commanding the Right Brake Lamp ON and OFF with a scan tool. The E5AB tail/stop lamp-right should turn ON and OFF while changing between the commanded states.
• If the E5AB tail/stop lamp-right is always ON or always OFF, refer to Right Brake Lamp Malfunction.
Circuit/System Testing
Left Brake Lamp Malfunction
1. Ignition OFF, disconnect the X409 inline harness connector at the E5E tail lamp-left.
2. Test for less than 30 ohm between the ground circuit terminal A and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal D and ground.
4. Ignition ON, command the Left Brake Lamp ON and OFF 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 control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the E5E tail lamp-left.
Right Brake Lamp Malfunction
1. Ignition OFF, disconnect the X410 inline harness connector at the E5F tail lamp-right.
2. Test for less than 30 ohm between the ground circuit terminal A and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal D and ground.
4. Ignition ON, command the Right Brake Lamp ON and OFF 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 control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the E5F tail lamp-right.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Tail Lamp Replacement Service and Repair
* Control Module References Control Module References for BCM replacement, programming and setup