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Tahoe / Yukon Service Manual

Horns Malfunction

Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions Diagnostic Fault Information

Circuit number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
3287 Signal B13E7 23 1 — —
28 Control B1008 11 B1008 13 B1008 12 —
29 Control 2 2 1 —
250 Ground — 2 — —
6051 Ground — 2 — —
1. P13 Horn= Always On 2. P13 Horn= Inoperative

Circuit/System Description The K9 Body Control Module provides the S33 Steering Wheel Horn Contact with signal circuit  3287. Ground is applied at all times to the S33 Steering Wheel Horn Contact. When the switch is pressed, ground is applied to the K9 Body Control Module through signal circuit 3287 indicating the horn switch has been activated. When the horn switch is active the K9 Body Control Module will connect the relay control circuit 28 to ground which will activate the KR3 Horn Relay. When the KR3 Horn Relay is active the contacts in the relay will close allowing voltage to flow through the relay to the P13 Horn causing the horn to operate. Ground is applied at all times to the P13 Horn. Diagnostic Aids Rotate the steering wheel while pressing the horn pad to identify intermittent and poor connections within the steering column. If the horn produces only a weak noise, inspect the following: Debris or water in the horn. Incorrect Mounting Refer to: Fastener Specifications. Debris on the component. Vehicle components that vibrate while the horn is sounding. R f I f ti Reference Information Schematic Reference Horn Schematics Connector End View Reference Master Electrical Component List Description and Operation Horns System Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Electrical Relay Replacement Scan Tool Reference Control Module References Circuit/System Verification

  1. Ignition » On / Vehicle » In Service Mode
  2. Press the appropriate button on the keyless entry transmitter Very the P13 Horn activates and emits a clear and even tone. ⇒ If the P13 Horn does not activate Refer to: Circuit/System Testing — Test 1 ⇒ P13 Horn — If an abnormal noise is present Refer to: Circuit/System Testing — Test 2 ⇓ If the P13 Horn activates & If no abnormal noise is present
  3. Operate the component: S33 Steering Wheel Horn Contact » Pressed Verify the component turns On and Off: P13 Horn ⇒ If the component does not turn On and Off Refer to: Circuit/System Testing — Test 3 ⇓ If the component turns On and Off
  4. A fault is not currently present and may be an intermittent condition Circuit/System Testing Test 1
  5. Ignition OFF, and all vehicle systems OFF. Disconnect the harness connector at the P13 Horn..
  6. Verify a test lamp illuminates between ground circuit terminal 1 and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on circuit 250 or the ground connection. ⇓ If the test lamp illuminates
  7. Connect a test lamp between the control circuit terminal 2 and ground, ignition ON.
  8. Verify the test lamp does not turn ON and OFF when pressing the S33 Steering Wheel Horn Contact ⇒ If the test lamp turns ON and OFF Test or replace the P13 Horn. ⇓ If the test lamp does not turn ON and OFF
  9. Ignition OFF, connect the harness connector at the P13 Horn. Disconnect the X2 harness connector at the X50A Engine Wiring Harness Junction Block, ignition ON.
  10. Verify the P13 Horn is not activated. ⇒ If the P13 Horn is activated 6.1. Ignition OFF, disconnect the harness connector at the P13 Horn, ignition ON. 6.2. 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. ⇓ If the P13 Horn is not activated
  11. Connect a 15 A fused jumper wire between the control circuit terminal G1 X2 and B+.
  12. Verify the P13 Horn activates. ⇒ If the P13 Horn does not activate 8.1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the P13 Horn, ignition ON. 8.2. 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 8.3. 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. ⇓ If the P13 Horn activates
  13. Ignition OFF, connect the X2 harness connector at the X50A Engine Wiring Harness Junction Block. Disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
  14. Verify the P13 Horn is not activated. ⇒ If the P13 Horn is activated 10.1. Ignition OFF, disconnect the X2 harness connector at the X50A Engine Wiring Harness Junction Block. 10.2. 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. ⇓ If the P13 Horn is not activated
  15. Connect a 3 A fused jumper wire between the control circuit terminal 11 X5 and ground.
  16. Verify the P13 Horn activates. ⇒ If the P13 Horn does not activate 12.1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the X50A  Engine Wiring Harness Junction Block, ignition ON. 12.2. 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. 12.3. 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 Engine Wiring Harness Junction Block. ⇓ If the P13 Horn activates
  17. Replace the K9 Body Control Module. Test 2
  18. Ignition/Vehicle & All vehicle systems » Off
  19. Disconnect the electrical connector: P13 Horn
  20. Verify a test lamp illuminates between ground circuit terminal 1 and B+. ⇒ If the test lamp does not illuminate 3.1. Repair the open/high resistance on circuit 250 or the ground connection. ⇓ If the test lamp illuminates
  21. Disconnect the electrical connector: X2 @ X50A Engine Wiring Harness Junction Block
  22. Test for less than 1 Ω between the test points: Control circuit terminal 2 @ Component harness & Control circuit terminal G1 @ Fuse/Junction Block Harness ⇒ If 1 Ω or greater ⇒ Repair the open/high resistance in the circuit. ⇓ If less than 1 Ω
  23. Test or replace the component: P13 Horn Test 3
  24. Ignition/vehicle OFF, disconnect the harness connector at the S33 Steering Wheel Horn Contact.
  25. Verify a test lamp illuminates between ground circuit terminal 1 and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on circuit 6051 or the ground connection. ⇓ If the test lamp illuminates
  26. Ignition/vehicle On.
  27. Verify the P13 Horn is not Active ⇒ If Active 4.1. Test the circuit 3287 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 4.2. Replace the K9 Body Control Module. ⇓ If Inactive
  28. Momentarily install a 3 A fused jumper wire between the signal circuit terminal 2 and ground.
  29. Verify the P13 Horn is Active ⇒ If the components do not sound and the 3 A fuse is OK 6.1. Test the circuit 3287 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 6.2. Replace the K9 Body Control Module. ⇒ If the components do not sound and the 3 A fuse is open 6.1. Test the circuit 3287 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 6.2. Replace the K9 Body Control Module. ⇓ If the components produces a sound
  30. Test or replace the S33 Steering Wheel Horn Contact. Component Testing P13 Horn
  31. Ignition/Vehicle » Off
  32. Disconnect the electrical connector: P13 Horn
  33. Connect a jumper wire between the test points: Ground terminal 1 & Ground
  34. Momentarily connect a 15 A fused jumper wire between the test points: Control terminal 2 & 12 V Verify the component turns On and Off when connecting and disconnecting the jumper wire: P13 Horn ⇒ If the component does not turn On and Off Replace the component: P13 Horn ⇓ If the component turns On and Off
  35. All OK. S33 Steering Wheel Horn Contact
  36. Ignition/Vehicle » Off
  37. Disconnect the electrical connector: S33 Steering Wheel Horn Contact
  38. Test for infinite resistance between the test points: Signal terminal 2 & Ground terminal 1 — S33 Steering Wheel Horn Contact » Not Pressed ⇒ If less than infinite resistance Replace the component: S33 Steering Wheel Horn Contact ⇓ If infinite resistance
  39. Test for less than 3 Ω between the test points: Signal terminal 2 & Ground terminal 1 — S33 Steering Wheel Horn Contact » Pressed ⇒ If 3 Ω or greater Replace the component: S33 Steering Wheel Horn Contact ⇓ If less than 3 Ω
  40. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Steering Wheel Airbag Replacement Horn Replacement Engine Wiring Harness Junction Block Replacement For control module replacement, programming, and setup refer to: Control Module References