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: Center High Mounted Stop Lamp (CHMSL) CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
MISC IGN Fuse B+ Supply | 1 | 1 | -- | -- |
Stop Lamp Switch 12V Reference | B3445 00 | 3 | -- | -- |
STOP LAMPS Fuse B+ Supply | 1 | 1 | -- | -- |
Left Outage Detection Signal | 1 | 1 | 1 | -- |
Left Outage Detection Signal -- European | 4 | 4 | 4 | -- |
Right Outage Detection Signal | 1 | 1 | 1 | -- |
Right Outage Detection Signal -- European | 4 | 4 | 4 | -- |
Stop Lamp Switch Signal | -- | 3 | 3 | -- |
Stop Lamp Switch Control | 1 | 1 | 1 | -- |
Center High Mounted Stop Lamp (CHMSL) Control | B3884 00 | 2 | 2 | -- |
Left Lower Tail/Stop and Turn Signal Lamp Control | 1 | 1 | 1 | -- |
Left Upper Tail/Stop and Turn Lamp Control | 1 | 1 | 1 | -- |
Left Tail Lamp Control Circuit Board Control | 1 | 1 | 1 | -- |
Left Tail Lamp Control Circuit Board Control -- European | 4 | 4 | 4 | -- |
Right Lower Tail/Stop and Turn Signal Lamp Control | 1 | 1 | 1 | -- |
Right Upper Tail/Stop and Turn Signal Lamp Control | 1 | 1 | 1 | -- |
Right Tail Lamp Control Circuit Board Control | 1 | 1 | 1 | -- |
Right Tail Lamp Control Circuit Board Control -- European | 4 | 4 | 4 | -- |
Center High Mounted Stop Lamp (CHMSL) Ground | -- | 2 | -- | -- |
Left Upper Tail/Stop and Turn Signal Lamp Ground | -- | 1 | -- | -- |
Left Tail Lamp Control Circuit Board Ground | -- | 1 | -- | -- |
Left Lower Tail/Stop and Turn Signal Lamp Ground | -- | 1 | -- | -- |
Left Tail/Stop Lamp Ground | -- | 1 | -- | -- |
Left Tail Lamp Circuit Board Ground -- European | -- | 4 | -- | -- |
Right Lower Tail/Stop and Turn Signal Lamp Ground | -- | 1 | -- | -- |
Right Lower Tail/Stop and Turn Signal Lamp Ground | -- | 1 | -- | -- |
Right Tail Lamp Control Circuit Board Ground | -- | 1 | -- | -- |
Right Tail/Stop Lamp Ground | -- | 1 | -- | -- |
Right Tail Lamp Circuit Board -- European | -- | 4 | -- | -- |
| ||||
Circuit/System Description
North American or European
The stop lamp switch is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a low reference signal and a B+ reference voltage to the stop lamp switch. When the stop lamp switch contacts close indicating the brakes have been applied, the BCM will apply battery voltage to stop lamp relay control circuit and the 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 to the STOP LAMPS fuse to illuminate the left and right stop lamps.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The stop lamps must be commanded ON. |
Conditions for Setting the DTC
The BCM detects a short to ground in the CHMSL supply voltage circuit when the stop lamps are commanded ON.
Action Taken When the DTC Sets
The CHMSL will not illuminate.
Conditions for Clearing the DTC
| • | The conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction-free ignition cycles. |
| • | The BCM receives the clear code command from the scan tool. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the center high mounted stop lamp.
- Test for less than 5.0 ohms between the ground circuit terminal B and ground.
- Connect a test lamp between the stop lamp control circuit terminal A and ground circuit terminal B.
- Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the center high mounted stop lamp.
| ⇒ | 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 |
