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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
STOP LAMP Fuse B+ | 1 | 1 | -- | -- |
VEH CHMSL Fuse B+ | 1 | 1 | 1 | -- |
VEH STOP Fuse B+ | 1 | 1 | 1 | -- |
Stop Lamp Switch Signal | 1 | 1 | 1 | -- |
Left Tail/Stop Lamp Circuit Ground | -- | 2 | -- | -- |
Right/Stop Lamp Circuit Ground | -- | 2 | -- | -- |
CHMSL Ground | -- | 2 | -- | -- |
1. Stop Lamp Switch Malfunction 2. Stop Lamp Malfunction | ||||
Circuit/System Description
The STOP fuse in the engine wiring harness junction block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the VEHICLE STOP fuse and the VEHICLE CHMSL fuse. The current flow is now to the stop lamps which are grounded at G401 and G402. The center high mounted stop lamp (CHMSL) is grounded at G401.
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 Verification
Press and release the brake pedal while observing brake lamp operation.
| ⇒ | If all of the brake lamps are always on or inoperative, refer to the Stop Lamp Switch Malfunction. |
| ⇒ | If 1 or 2 of the brake lamps function normally, refer to the Stop Lamp Malfunction. |
Circuit/System Testing
Stop Lamp Switch Malfunction
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Test for less than 5.0 ohms between the low reference circuit terminal A.
- Verify that a test lamp illuminates between the B+ circuit terminal B and ground.
- Install a 25A fused jumper wire between the stop lamp control circuit terminal A and the B+ circuit terminal B. Verify the stop lamps are illuminated.
- If all circuits test normal, replace the stop lamp switch.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, and the B+ circuit fuse is open, test the stop lamp control circuit terminal A for a short to ground. |
| ⇒ | If the stop lamps are not illuminated, test the stop lamp control circuit for a short to ground or an open/high resistance. |
Stop Lamp Malfunction
- Ignition OFF, remove the fuse of the inoperative STOP/CHMSL lamp and inspect.
- Ignition OFF, disconnect the harness connector at the inoperative stop lamp.
- Test for less than 5.0 ohms between the listed ground circuit terminal and ground.
- Connect a test lamp between the listed stop lamp control circuit terminal and ground.
- 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 inoperative stop lamp.
| ⇒ | If the fuse is OPEN, test the appropriate control circuit of the blown fuse for a short to ground. |
| • | Center High Mounted Stop Lamp terminal B |
| • | Tail/Stop Lamp terminal GRD |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Center High Mounted Stop Lamp terminal A |
| • | Tail/Stop Lamp terminal MJR |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
