For 1990-2009 cars only
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 |
|---|---|---|---|---|
Brake Lamp Switch Voltage Supply Circuit | 2 | 2 | -- | -- |
Brake Lamp Switch Signal Circuit | 2 | 2 | 1 | -- |
Brake Lamp Bulb Ground Circuit | -- | 2 | -- | -- |
Stop Lamp Switch | 2 | 2 | 1 | -- |
1. Brake Lamps Always ON 2. Brake Lamps Inoperative | ||||
Circuit/System Description
The stop lamp switch is supplied voltage by the brake fuse. When the brake pedal is pressed the stop lamp switch closes supplying voltage to the stop lamp light bulbs.
Diagnostic Aids
| • | Verify that the stop lamp bulbs are working properly. |
| • | A short to ground, a short to voltage in the following location may cause a malfunction to occur: |
| - | The brake switch supply circuit |
| - | The brake switch ground circuit |
| - | The brake switch |
Reference Information
Schematic Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Engage the brake pedal, observe the brake lights. The brake lights should turn ON when the brake pedal is depressed.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Verify that a test lamp illuminates between the voltage supply circuit and ground.
- Install a 3-amp fused jumper wire between the signal circuit and the voltage supply circuit. Verify that the stop lamps are ON.
- If all circuits test normal, test or replace the stop lamp switch.
| ⇒ | If the test lamp does not illuminate, repair the voltage supply circuit for a short to ground or an open/high resistance. If the voltage supply circuit fuse is open, also test the signal circuit for a short to ground. |
| ⇒ | If the stop lamps are not ON, test the signal circuit for an open/high resistance. If circuit tests normal, test or replace the brake lamp bulb. |
Component Testing
- Ignition OFF, disconnect the harness connector at the stop lamp switch.
- Test for infinite resistance between the signal terminal and the voltage supply terminal with the switch in the open position.
- Test for less than 1 ohm of resistance between the signal terminal and the voltage supply terminal with the switch in the closed position.
| ⇒ | If less than infinite resistance, replace the stop lamp switch. |
| ⇒ | If greater than 1 ohm, replace the stop lamp switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
