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Home >> Cadillac >> 2008 >> XLR Base >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel System Displays & Gages >> Diagnostic Information and Procedures >> Head Up Display (HUD) Inoperative >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the dimming/head-up display (HUD) switch.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal 1 and ground.
    • If greater than 1 ohm, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Dim Select Switch parameter in the IPC Data List is Inactive.
    • If not Inactive, test the dimmer/HUD down switch signal circuit terminal 3 or dimmer/HUD up switch signal circuit terminal 2 for a short to ground. If the circuits test normal, replace the HUD.
  4. Install a 3A fused jumper wire between the dimmer/HUD up switch signal circuit terminal 2 or dimmer/HUD down switch signal circuit terminal 3 and the ground circuit terminal 1. Verify the scan tool Dim Up Switch and Dim Down Switch parameter in the IPC Data List is Active.
    • If any is not Active, test the appropriate switch signal circuit for a short to voltage or an open/high resistance. If the circuits tests normal, replace the HUD.
  5. Ignition OFF, disconnect the harness connector at the HUD.
  6. Test for less than 1 ohm of resistance between the HUD ground circuit terminal 10 and ground.
    • If greater than 1 ohm, test the ground circuit for an open/high resistance.
  7. Ignition ON, verify a test lamp illuminates when connected between the battery positive voltage circuit terminal 1 and the ground circuit terminal 10.
    • If the test light does not illuminate, test the HUD battery positive voltage circuit for a short to ground or an open/high resistance.
  8. If all circuits test normal, test or replace the dimmer/HUD switch.
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