Circuit/System Testing: Notes

Headlamp Switch Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal C.
   • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Headlamp Switch parameter is Inactive.
   • If not the specified value, test the headlamp ON switch signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the headlamp ON switch signal circuit terminal D and the ground circuit terminal C. Verify the scan tool Headlamp Switch parameter is Active.
   • If not the specified value, test the headlamp ON switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the headlamp switch.

Turn Signal/Multifunction Switch Malfunction

1. Ignition OFF, disconnect the X2 harness connector at the turn signal multifunction switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal A.
   • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool High Beam Switch parameter is OFF.
   • If not the specified value, test the high beam switch signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.
4. Ignition ON, verify the scan tool Flash to Pass parameter is OFF.
   • If not the specified value, test the flash to pass switch signal circuit terminal B for a short to ground. If the circuit tests normal, replace the BCM.
5. Install a 3A fused jumper wire between the high beam switch signal circuit terminal C and the ground circuit terminal A. Verify the scan tool High Beam Switch parameter is ON.
   • If not the specified value, test the high beam switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
6. Install a 3A fused jumper wire between the flash to pass switch signal circuit terminal B and the ground circuit terminal A. Verify the scan tool Flash to Pass Switch parameter is ON.
   • If not the specified value, test the flash to pass switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
7. If all circuits test normal, test or replace the turn signal/multifunction switch.

Low Beam Headlamp Malfunction

1. Ignition OFF, disconnect the HDM relay.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 6.
   • If the test lamp does not illuminate, 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 4 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 2 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 4 for a short to ground.
5. Disconnect the harness connector at the inoperative low beam headlamp.
6. Test for less than 5.0 ohms between B+ and the ground circuit terminal B.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect a 15A fused jumper wire between the B+ circuit terminal 2 and the low beam headlamp control circuit terminal 4. Verify the low beam headlamps are ON.
   • If the headlamps are always OFF, test the control circuit for a short to ground or an open high resistance.
   • If the headlamps are always ON, test the control circuit for short to voltage.
8. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
9. Command the low beam headlamps ON and OFF with the headlamp switch. The test lamp should turn ON and OFF between the commanded states.
   • 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 BCM.
   • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
10. If all circuits test normal, test or replace the HDM relay.

High Beam Headlamp Malfunction

1. Ignition OFF, disconnect the HI HEADLAMP relay.
2. Ignition ON, 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.
3. 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.
4. 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 a short to ground or an open/high resistance.
5. Ignition OFF, disconnect the harness connector at the inoperative high beam headlamp.
6. Verify that a test lamp illuminates between B+ and the high beam headlamp ground circuit terminal B.
   • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the inoperative high beam headlamp.
8. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the high beam headlamps are activated.
   • If the high beam headlamps do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the inoperative high beam headlamp.
9. Connect a test lamp between the B+ circuit terminal 30 and the relay control circuit terminal 86.
10. Turn the high beam headlamps ON and OFF. 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 BCM.
    • 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 BCM.
11. If all circuits test normal, test or replace the HI HEADLAMP relay.