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Circuit/System Testing

WARNING: This page is about a different car, the 2016 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

Horn Switch Malfunction

  1. Ignition OFF and all vehicle systems OFF, disconnect the X1 and X2 harness connectors at the S33 Horn Switch. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 1 X2 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Verify the scan tool Horn Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 1 X1 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • If Inactive 
  5. Install a 3 A fused jumper wire between the signal circuit terminal 1 X1 and the ground circuit terminal 1 X2 .
  6. Verify the scan tool Horn Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If Active 
  7. Test or replace the S33 Horn Switch.

Horns or Horn Command Malfunction

  1. Ignition OFF, and all vehicle systems OFF. Disconnect the harness connector at the P13 Horn Assembly. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 1 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  3. Connect a test lamp between the control circuit terminal 2 and ground, ignition ON.
  4. Verify the test lamp does not turn ON and OFF when commanding the Horn Relay On and Off with a scan tool.
    • If the test lamp turns ON and OFF 

      Test or replace the P13 Horn Assembly.

    • If the test lamp does not turn ON and OFF 
  5. Ignition OFF, connect the harness connector at the P13 Horn Assembly. Disconnect the X1 harness connector at the X50A Fuse Block-Underhood, ignition ON.
  6. Verify the P13 Horn Assembly is not activated.
    • If the P13 Horn Assembly is activated 
    1. Ignition OFF, disconnect the harness connector at the P13 Horn Assembly, ignition ON.
    2. Test for less than 1 V between the control circuit terminal 2 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, test or replace the P13 Horn Assembly.
    • If the P13 Horn Assembly is not activated 
  7. Connect a 15 A fused jumper wire between the control circuit terminal 27 and B+.
  8. Verify the P13 Horn Assembly activates.
    • If the P13 Horn Assembly does not activate 
    1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the P13 Horn Assembly, ignition ON.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than Infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the P13 Horn Assembly.
    • If the P13 Horn Assembly activates 
  9. Ignition OFF, connect the X1 harness connector at the X50A Fuse Block-Underhood. Disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
  10. Verify the P13 Horn Assembly is not activated.
    • If the P13 Horn Assembly is activated 
    1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block-Underhood.
    2. Test for infinite resistance between the K9 Body Control Module control circuit terminal 19 X5 and ground.
      • If less than Infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the K9 Body Control Module.
    • If the P13 Horn Assembly is not activated 
  11. Connect a 3 A fused jumper wire between the control circuit terminal 19 and ground.
  12. Verify the P13 Horn Assembly activates.
    • If the P13 Horn Assembly does not activate 
    1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the X50A Fuse Block-Underhood, ignition ON.
    2. Test for less than 1 V between the K9 Body Control Module control circuit terminal 19 X5 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the X50A Fuse Block-Underhood.
    • If the P13 Horn Assembly activates 
  13. Replace the K9 Body Control Module.

Horn - Poor Tone

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the P13 Horn Assembly. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 1 Ω between the ground circuit terminal 1 and ground.
    • If 1 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the high resistance in the circuit.
      • If less than 2 Ω, repair high resistance in the ground connection.
    • If less than 1 Ω 
  3. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block-Underhood.
  4. Test for less than 2 Ω between the P13 Horn Assembly control circuit terminal 2 and the X50A Fuse Block-Underhood control circuit terminal 27 X1.
    • If 2 Ω or greater 

      Repair the high resistance in the control circuit.

    • If less than 2 Ω 
  5. Test or replace the P13 Horn Assembly.
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