Stop Lamps Always on

STOP LAMPS ALWAYS ON

DIAGNOSTIC FAULT INFORMATION




Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure Initial Inspection and Diagnostic Overview.

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
A short to ground, a short to voltage in the following location may cause a malfunction to occur:
- The brake switch ground circuit
- The brake switch

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
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Verify that the stop lamps are OFF.
- If the stop lamps are not OFF, test the stop lamp signal circuits for a short to voltage.
3. Verify that a test lamp illuminates between the voltage supply circuit and ground.
- 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, test or replace the stop lamp switch.
4. Install a 3-amp fused jumper wire between the signal circuit and the voltage supply circuit. Verify that the brake lamps are ON.
- If the brake lamps are not ON, test the signal circuit for an open/high resistance. If circuit tests normal, test or replace the brake lamp bulb.
5. If all circuits test normal, test or replace the stop lamp switch.

COMPONENT TESTING

Stop Lamp Switch Testing
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Test for infinite resistance between the signal terminal and the voltage supply terminal with the switch in the open position.
- If less than infinite resistance, replace the stop lamp switch.
3. 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 greater than 1 ohm, replace the stop lamp switch.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Stop Lamp Switch Adjustment
- Stop Lamp Switch Replacement Verification Tests