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 B3884 00: Stop Lamp CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Center High Mounted Stop Lamp (CHMSL) Control | B3445 00, B3884, 00 | 2, 3 | 2, 3 | -- |
Brake Position Sensor Signal | C0277 06, 07 | C0277 06 | C0277 07 | C0277 09 |
Stop Lamp Relay Control - Export | B3445 00 | 2, 3 | 2, 3 | -- |
Stop Lamp Relay Switch B+ - Export | 2 | 2 | -- | -- |
Brake Position Sensor 5-Volt Reference | C0277 06, C0890 03 | C0277 06, C0890 03 | C0890 07 | -- |
Brake Position Sensor Low Reference | -- | C0277 06 | C0277 07 | -- |
Left Rear Stop/Turn Lamp Supply Voltage | 1, 2 | 1, 2 | 1, 2 | -- |
Right Rear Stop/Turn Lamp Supply Voltage | 1, 2 | 1, 2 | 1, 2 | -- |
Center High Mounted Stop Lamp (CHMSL) Ground | -- | 3 | 3 | -- |
Left Rear Stop/Turn Lamp Ground | -- | 1, 2 | 1, 2 | -- |
Right Rear Stop/Turn Lamp Ground | -- | 1, 2 | 1, 2 | -- |
Stop Lamp Relay Ground - Export | -- | 2 | 2 | -- |
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Circuit/System Description
Domestic
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. For more detailed information concerning stop lamp operation refer to Exterior Lighting Systems Description and Operation .
Export
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 stop lamp relay coil side control circuit, transmission control module (TCM), engine control module (ECM), and center high mounted stop lamp (CHMSL). When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage from the STOP LAMPS fuse to illuminate the rear stop lamps and trailer stop lamps. For more detailed information concerning stop lamp operation refer to Exterior Lighting Systems Description and Operation .
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
DTC B3884 00 will set when the BCM detects a short to ground in the CHMSL control circuit when the stop lamps are being commanded ON.
Actions Taken When the DTC Sets
The BCM will not illuminate the CHMSL.
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. |
Diagnostic Aids
Important: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .
Reference Information
Schematic Reference
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the CHMSL.
- Ignition OFF, test for less than 50.0 ohms of resistance between the ground circuit terminal B and ground.
- Connect a test lamp between the control circuit terminal A and the ground circuit terminal B.
- Ignition ON, command the stop lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the CHMSL.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the 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 BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
