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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 108 (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 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

Test 1

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector : P13 Horn Assembly
  3. Test for less than 1 ohms between the test points : Ground circuit terminal A & Ground
    • If 1 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 1 ohms between the test points : Ground circuit terminal A & Ground Connection
      • If 1 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 1 ohms - Repair the open/high resistance in the ground connection.
    • Go to next step : If less than 1 ohms 
  4. Verify the fuse is not open : F16UA Fuse
    • If the fuse is open 
    1. Replace the component : F16UA Fuse
    2. Verify the fuse does not open.
      • If the fuse opens - Test or replace the component : X50A Fuse Block - Underhood
      • If the fuse does not open, go to the next step.
    • Go to next step : If the fuse is not open 
  5. Connect a test lamp between the test points : Control circuit terminal B & Ground circuit terminal A
  6. Ignition - On / Vehicle - In Service Mode
  7. Perform the scan tool control function : Horn Relay Command - On and Off

    Verify the test lamp does not turn On and Off.

    • If the test lamp turns On and Off 

      Test or replace the component : P13 Horn Assembly

    • Go to next step : If the test lamp does not turn On and Off 
  8. Ignition/Vehicle - Off
  9. Connect the electrical connector : P13 Horn Assembly
  10. Disconnect the electrical connector : X50A Fuse Block - Underhood
  11. Ignition - On / Vehicle - In Service Mode
  12. Momentarily connect a 15 A fused jumper wire between the test points : Control circuit terminal B4 X1 & B+

    Verify the component turns On and Off when connecting and disconnecting the jumper wire : P13 Horn Assembly

    • If the component does not turn On and Off 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector : P13 Horn Assembly
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points : Control circuit terminal B @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step : If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for infinite resistance between the test points : Control circuit terminal B @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step : If infinite resistance
    7. Test for less than 2 ohms between the test points : Control circuit terminal B @ Component harness & Control circuit terminal B4 X1 @ Fuse Block Harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Test or replace the component : P13 Horn Assembly
    • Go to next step : If the component turns On and Off 
  13. Ignition/Vehicle & All vehicle systems - Off
  14. Verify the fuse is not open : F16UA Fuse
    • If the fuse is open 

      Test or replace the component : X50A Fuse Block - Underhood

    • Go to next step : If the fuse is not open 
  15. Connect the electrical connector : X50A Fuse Block - Underhood
  16. Disconnect the electrical connector : K9 Body Control Module
  17. Ignition - On / Vehicle - In Service Mode
  18. Momentarily connect a 3 A fused jumper wire between the test points : Control circuit terminal 18 X5 & Ground

    Verify the component turns On and Off when connecting and disconnecting the jumper wire : P13 Horn Assembly

    • If the component does not turn On and Off 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector : X50A Fuse Block - Underhood
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points : Control circuit terminal 18 X5 @ Control module harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step : If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for infinite resistance between the test points : Control circuit terminal 18 X5 @ Control module harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step : If infinite resistance
    7. Test for less than 2 ohms between the test points : Control circuit terminal 18 X5 @ Control module harness & Terminal H3 X3 @ Fuse Block Harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Test or replace the component : X50A Fuse Block - Underhood
    • Go to next step : If the component turns On and Off 
  19. Replace the component : K9 Body Control Module

Test 2

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector : P13 Horn Assembly
  3. Test for less than 1 ohms between the test points : Ground circuit terminal A & Ground
    • If 1 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 1 ohms between the test points : Ground circuit terminal A & Ground Connection
      • If 1 ohms or greater - Repair the open/high resistance in the circuit.
    • Go to next step : If less than 1 ohms 
  4. Disconnect the electrical connector : X1 @ X50A Fuse Block - Underhood
  5. Test for less than 1 ohms between the test points : Control circuit terminal B @ Component harness & Control circuit terminal B4 X1 @ Fuse 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 : P13 Horn Assembly

Test 3

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector : S33 Horn Switch
  3. Test for less than 10 ohms between the test points : Ground circuit terminal B & Ground
    • If 10 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 2 ohms between the test points : Ground circuit terminal B & Ground Connection
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
    • Go to next step : If less than 10 ohms 
  4. Ignition - On / Vehicle - In Service Mode
  5. Verify the component is not activated : P13 Horn Assembly
    • If the component activates 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector : X3 @ X50A Fuse Block - Underhood
    3. Test for infinite resistance between the test points : Control circuit terminal A @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component : X50A Fuse Block - Underhood
    • Go to next step : If the component does not activate 
  6. Connect a 3 A fused jumper wire between the test points : Control circuit terminal A & Ground circuit terminal B
  7. Verify the component activates : P13 Horn Assembly
    • If the component does not activate 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector : X50A Fuse Block - Underhood
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points : Control circuit terminal A @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step : If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points : Control circuit terminal 2 @ Component harness & Terminal H3 X3 @ Fuse Block Harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component : X50A Fuse Block - Underhood
    • Go to next step : If the specified state 
  8. Test or replace the component : S33 Horn Switch
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