Circuit/System Testing

Stop Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 Ω between the ground circuit terminal 2 and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool EBCM BPP signal parameter is Released.
   • If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the EBCM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the ground circuit terminal 2. Verify the scan tool EBCM BPP signal parameter is Applied.
   • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the EBCM.
5. Verify the stop lamps and center high mounted stop lamp are illuminated.
   • If not the specified value, test the signal circuit for a short to ground or an open/high resistance.
6. If all circuits test normal, test or replace the stop lamp switch.

Stop Lamp Malfunction

1. Ignition OFF, disconnect the VSES/STOP relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
   • 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 control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the VSES/STOP relay.
3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
   • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Turn the stop lamp switch ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.
   • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the stop lamp switch.
   • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the stop lamp switch.
6. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
   • If the test lamp illuminates, test the control circuit for a short to voltage.
7. Ignition OFF, disconnect the harness connector at the appropriate tail/stop lamp.
8. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 Ω between the tail/stop lamp ground circuit terminal G and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
9. Connect the harness connector at the tail/stop lamp.
10. Ignition ON, connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the tail/stop lamp is activated.
    • If the tail/stop lamp does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the tail/stop lamp.
11. If all circuits test normal, test or replace the VSES/STOP relay.

Center High Mounted Stop Lamp Malfunction

1. Ignition OFF, disconnect the VSES/STOP relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
   • 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 control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the VSES/STOP relay.
3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
   • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Turn the stop lamp switch ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.
   • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the stop lamp switch.
   • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the stop lamp switch.
6. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
   • If the test lamp illuminates, test the control circuit for a short to voltage.
7. Ignition OFF, disconnect the harness connector at the center high mounted stop lamp.
8. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 Ω between the tail/stop lamp ground circuit terminal B and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
9. Connect the harness connector at the center high mounted stop lamp.
10. Ignition ON, connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the center high mounted stop lamp is activated.
    • If the center high mounted stop lamp does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the center high mounted stop lamp.
11. If all circuits test normal, test or replace the VSES/STOP relay.