Circuit/System Testing

HUD Inoperative

1. Ignition OFF, disconnect the harness connector at the HUD switch.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 3 and ground.
   • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HUD.
3. Verify the scan tool Display Dimming parameter is greater than 98 percent.
   • If less than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the HUD.
4. Install a 3A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 3. Verify the scan tool Display Dimming parameter is less than 2 percent.
   • If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the HUD.
5. If all circuits test normal, test or replace the HUD switch.

HUD Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the HUD switch assembly.
2. Ignition OFF, test for less than 5 ohms between the low reference terminal 3 and ground.
   • If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Ignition ON, verify that all of the scan tool HUD Switch parameters are Inactive.
   • If any is not Inactive, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the HUD.
4. Ignition ON, install a 3-amp fused jumper wire between the signal circuit terminal 6 and ground. Verify the scan tool HUD Switch parameters are Active.
   • If any are not Active, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HUD.
5. If all the circuits test normal, test or replace the HUD switch assembly.