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 R12 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 R10 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 R12 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 R11 and ground.
   • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Ignition OFF, disconnect the harness connector at the horn assembly.
6. Test for less than 1.0 ohm of resistance between the horn assembly 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 assembly.
8. Ignition ON, connect a 15A fused jumper wire between the B+ circuit terminal R11 and the control circuit terminal R12. Verify the horn is activated.
   • If the horn does not activate, does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the horn assembly.
9. Connect a test lamp between the B+ circuit terminal R10 and the control circuit terminal R13.
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 assembly.
2. Test for less than 1.0 ohm of resistance 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 harness connector X1 at the underhood fuse block.
4. Test for less than 1.0 ohm of resistance between the control circuit terminal 4 at the underhood fuse block and the control circuit terminal B at the horn assembly.
   • 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 assembly.

Horn Circuit Test

1. Ignition OFF, disconnect the HORN relay.
2. Connect a test lamp between the B+ circuit terminal R10 and the control circuit terminal R13.
3. Ignition ON, command the horn 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 is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the IPM.

• 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, replace the IPM.