Circuit/System Testing

DRL Relay Circuit Testing

1. Ignition OFF, disconnect the DRL PCB relay underhood fuseblock terminals C2 pin 38 coil side and underhood fuseblock terminal C3 pin 15 switch side.
2. Ignition ON, verify the DRLs are deactivated.
   • If the DRLs are still activated, replace the underhood fuseblock.
3. Verify that a test lamp illuminates between the DRL PCB relay coil voltage supply circuit, check the underhood fuseblock terminal B+ feed of the underhood fuseblock and ground.
   • If the test lamp does not illuminate, replace the underhood fuseblock. If the voltage supply circuit fuse is open, replace the underhood fuseblock.
4. Verify that a test lamp illuminates between the DRL PCB relay switch voltage supply circuit, check the underhood fuseblock B+ voltage feed supply circuit and ground.
   • If the test lamp does not illuminate, replace the underhood fuseblock.
5. Connect a 15-amp fused jumper wire between the underhood fuseblock B+ feed and the relay switch control circuit underhood fuseblock terminal C2 pin 38. Verify the DRLs are activated.
   • If the DRLs are not activated, replace the underhood fuseblock.
6. Connect a test lamp between the relay coil control circuit, underhood fuseblock terminal C2 pin 38 and the relay coil voltage supply circuit, use the underhood fuseblock B+ feed terminal.
7. Command the DRL relay 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 remains ON all the time, test for a short to ground on the relay coil control circuit. If the circuit tests normal, replace the BCM.
   • If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the relay coil control circuit. If the circuit tests normal, replace the BCM.
8. If all circuits test normal, test or replace the underhood fuseblock.