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 Switch B+ | 1 | 1 | -- | -- |
Stop Lamp Control | 1 | 1 | 1 | -- |
Stop Lamp Ground - Left | 1 | 1 | -- | -- |
Stop Lamp Ground - Right | -- | 1 | -- | -- |
Center High Mounted Stop Lamp (CHMSL) Ground - Left | -- | 1 | -- | -- |
Center High Mounted Stop Lamp (CHMSL) Ground - Right | -- | 1 | -- | -- |
1. Stop Lamps Malfunction | ||||
Circuit/System Description
The STOP fuse in the underhood fuse block supplies battery voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery voltage is supplied to the electronic brake control module (EBCM), powertrain control module (PCM), left and right stop lamps, and the center high mounted stop lamp (CHMSL). The stop and CHMSL lamps are grounded at all times at G105.
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
Stop Lamp Circuit Test
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.
- Connect the harness connector at the stop lamp switch.
- Disconnect the harness connector at the inoperative stop lamp.
- Test for less than 5 ohms between the listed ground circuit terminal and ground.
- Connect a test lamp between the control circuit terminal A and ground. Press and release the brake pedel. The test lamp should turn ON and OFF.
- If all circuits test normal, replace the inoperative stop lamp.
| ⇒ | 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 signal circuit terminal 2 for a short to ground. |
| • | Left or Right stop lamp terminal G |
| • | Left or Right CHMSL terminal B |
| ⇒ | 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 terminal for a short to voltage. |
| ⇒ | If the test lamp is always OFF, test the control circuit terminal for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
