Circuit/System Testing

Stop Lamps Malfunction

1. Ignition OFF, disconnect the stop lamp relay.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal R36 and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal R38 and ground.
   • If the test lamp illuminates, test the control circuit for a short to voltage.
4. Verify that a test lamp illuminates between the B+ circuit terminal R37 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 relay control circuit terminal R38 for a short to ground. If the circuit tests normal, test or replace the stop lamp relay.
5. Disconnect the harness connector at the inoperative stop lamp.
6. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal D and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the inoperative stop lamp.
8. Connect a 10A fused jumper wire between the B+ circuit terminal R37 and the control circuit terminal R38. Verify the stop lamps are activated.
   • If the stop lamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative stop lamp.
9. Connect a test lamp between the control circuit terminal R40 and the ground circuit terminal R36.
10. Ignition ON, command the stop lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the IPM.
    • 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 IPM.
11. If all circuits test normal, test or replace the stop lamp relay.

Center High Mounted Stop Lamp (CHMSL) Malfunction

1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal B and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal A and the ground circuit terminal B.
4. Ignition ON, command the stop lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
   • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the IPM.
   • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPM.
5. If all circuits test normal, test or replace the CHMSL.

Brake Pedal Position Sensor (BPPS) Malfunction

1. Ignition OFF, disconnect the harness connector at the BPPS.
2. Ignition ON, verify that a test lamp does not illuminate between the low reference circuit terminal A and ground.
   • If the test lamp illuminates, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the IPM.
3. Ignition ON, test for 4.8 volts and 5.2 volts between the 5-volt reference circuit terminal C and ground.
   • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPM.
   • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the IPM.
4. If all circuits test normal, replace the BPPS.