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Home >> Hummer >> 2008 >> H3 Base, Automatic >> Repair and Diagnosis >> Electrical >> Horns >> Diagnostic Information and Procedures >> Horns Malfunction >> Circuit/System Testing

Circuit/System Testing

Horn Switch Circuit Test

  1. Ignition OFF, disconnect the HORN 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 85 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 HORN fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the HORN relay.
  4. 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 an open/high resistance.
  5. Disconnect the harness connector at the horn.
  6. Test for less than 1.0 ohm between the horn ground circuit terminal A and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the horn.
  8. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the horn is activated.
    • If the horn does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the horn.
  9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  10. Press and release the steering wheel horn pad. 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, inspect for a sticking horn switch.
    • 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, inspect for an open horn switch.
  11. If all circuits test normal, test or replace the HORN relay.

Horn - Poor Tone

  1. Ignition OFF, disconnect the harness connector at the horn.
  2. Test for less than 1 ohm between the horn ground circuit terminal A and ground.
    • If greater than the specified range, test the ground circuit for a high resistance.
  3. Disconnect the X2 harness connector at the underhood fuse block.
  4. Test for less than 1 ohm between the control circuit terminal 9 at the underhood fuse block and the control circuit terminal B at the horn.
    • If greater than the specified range, test the control circuit for a high resistance.
  5. If all circuits test normal, test or replace the horn.
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