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Home >> Cadillac >> 2021 >> CT4 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 202 (Horns And Pedestrian Alerts) >> Diagnostic Information and Procedures >> Horns Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

Test 1

  1. Ignition OFF, and all vehicle systems OFF. Disconnect the harness connector at the P12A Horn - High Note or P12B Horn - Low Note. It may take up to 2 min for all vehicle systems to power down.
  2. Connect a test lamp between the control circuit terminal 2 and ground, ignition ON.
  3. Operate the component: S33 Steering Wheel Horn Contact - Pressed
    • If the test lamp turns ON and OFF 

      Test or replace the P12A Horn - High Note or P12B Horn - Low Note.

    • Go to next step: If the test lamp does not turn ON and OFF 
  4. Ignition OFF, connect the harness connector at the P12A Horn - High Note or P12B Horn - Low Note. Disconnect the X1 harness connector at theX50A Engine Wiring Harness Junction Block, ignition ON.
  5. Verify the P12A Horn - High Note and P12B Horn - Low Note are not activated.
    • If the P12A Horn - High Note and P12B Horn - Low Note are activated 
    1. Ignition OFF, disconnect the harness connector at the P12A Horn - High Note or P12B Horn - Low Note, 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 P12A Horn - High Note and P12B Horn - Low Note.
    • Go to next step: If the P12A Horn - High Note and P12B Horn - Low Note are not activated 
  6. Connect a 15 A fused jumper wire between the control circuit terminal F2 X1 and B+.
  7. Verify the P12A Horn - High Note and P12B Horn - Low Note activates.
    • If the P12A Horn - High Note and P12B Horn - Low Note do not activate 
    1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the P12A Horn - High Note and P12B Horn - Low Note, 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.
      • Go to next step: 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 P12A Horn - High Note and P12B Horn - Low Note.
    • Go to next step: If the P12A Horn - High Note and P12B Horn - Low Note are activated 
  8. Ignition OFF, connect the X1 harness connector at the X50A Engine Wiring Harness Junction Block. Disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
  9. Verify the P12A Horn - High Note and P12B Horn - Low Note are not activated.
    • If the P12A Horn - High Note and P12B Horn - Low Note are activated 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Engine Wiring Harness Junction Block.
    2. Test for infinite resistance between the K9 Body Control Module control circuit terminal 11 X5 and ground.
      • If less than Infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the X50A Engine Wiring Harness Junction Block.
    • Go to next step: If the P12A Horn - High Note and P12B Horn - Low Note are not activated 
  10. Connect a 3 A fused jumper wire between the control circuit terminal 11 X5 and ground.
  11. Verify the P12A Horn - High Note and P12B Horn - Low Note are activated.
    • If the P12A Horn - High Note and P12B Horn - Low Note do not activate 
    1. Ignition OFF, remove the jumper wire, disconnect the X1 harness connector at the X50A Engine Wiring Harness Junction Block, ignition ON.
    2. Test for less than 1 V between the K9 Body Control Module control circuit terminal 11 X5 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: 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, replace the X50A Engine Wiring Harness Junction Block.
    • Go to next step: If the P12A Horn - High Note and P12B Horn - Low Note activates 
  12. Replace the K9 Body Control Module.

Test 2

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector: P12A Horn - High Note or P12B Horn - Low Note
  3. Verify a test lamp illuminates between ground circuit terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 550 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  4. Disconnect the electrical connector: X1 @ X50A Engine Wiring Harness Junction Block
  5. Test for less than 1 ohms between the test points: Control circuit terminal 2 @ Component harness & Control circuit terminal F2 @ Fuse/Junction Block Harness
    • If 1 ohms or greater 
    • Repair the open/high resistance in the circuit.
    • Go to next step: If less than 1 ohms 
  6. Test or replace the component: P12A Horn - High Note or P12B Horn - Low Note

Test 3

  1. Ignition/vehicle OFF, disconnect the\ connector at the S33 Steering Wheel Horn Contact.
  2. Verify a test lamp illuminates between ground circuit terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 1351 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Ignition/vehicle On.
  4. Verify the P12A Horn - High Note & P12B Horn - Low Note are not Active
    • If Active 
    1. Test the circuit 3287 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found.
    2. Replace the K9 Body Control Module.
    • Go to next step: If Inactive 
  5. Momentarily install a 3 A fused jumper wire between the signal circuit terminal 2 and ground.
  6. Verify the P12A Horn - High Note & P12B Horn - Low Note are Active
    • If the components do not sound and the 3 A fuse is OK 
    1. Test the circuit 3287 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found.
    2. Replace the K9 Body Control Module.
    • If the components do not sound and the 3 A fuse is open 
    1. Test the circuit 3287 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    2. Replace the K9 Body Control Module.
    • Go to next step: If the components produces a sound 
  7. Test or replace the S33 Steering Wheel Horn Contact.
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