LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 274 (Lighting System - DTC B3891 To DTC C0297 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Trailer Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

Trailer Backup Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  2. Test for less than 5 Ω between the ground circuit terminal 1 X2 and ground.
    • If 5 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 5 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
    • X1 terminal 13
    • X2 terminal 3
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the appropriate harness connector at the X53A Fuse Block - Rear Body.
    2. Test for infinite resistance between the B+ circuit terminal 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, replace the X53A Fuse Block - Rear Body.
    • If the test lamp illuminates 
  5. Ignition OFF, connect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  6. Connect a test lamp between the trailer backup lamp control circuit (5189 GN/WH) at the W8 Blunt Cut Trailer Provision and ground, ignition ON.
  7. Verify the test lamp turns ON and OFF when commanding the Trailer Backup Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module.
    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, replace the K68 Trailer Lighting Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K68 Trailer Lighting Control Module.
    • If the test lamp turns ON and OFF 
  8. Test or replace the W8 Blunt Cut Trailer Provision.

Trailer Fog Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  2. Test for less than 5 Ω between the ground circuit terminal 1 X2 and ground.
    • If 5 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 5 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
    • X1 terminal 13
    • X2 terminal 3
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the appropriate harness connector at the X53A Fuse Block - Rear Body.
    2. Test for infinite resistance between the B+ circuit terminal 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, replace the X53A Fuse Block - Rear Body.
    • If the test lamp illuminates 
  5. Ignition OFF, connect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  6. Connect a test lamp between the trailer fog lamp control circuit (5190 YE/WH) at the W8 Blunt Cut Trailer Provision and ground, ignition ON.
  7. Verify the test lamp turns ON and OFF when commanding the Trailer Fog Lamp(s) ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module.
    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, replace the K68 Trailer Lighting Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K68 Trailer Lighting Control Module.
    • If the test lamp turns ON and OFF 
  8. Test or replace the W8 Blunt Cut Trailer Provision.

Trailer Tail Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  2. Test for less than 5 Ω between the ground circuit terminal 1 X2 and ground.
    • If 5 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 5 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
    • X1 terminal 13
    • X2 terminal 3
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the appropriate harness connector at the X53A Fuse Block - Rear Body.
    2. Test for infinite resistance between the B+ circuit terminal 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, replace the X53A Fuse Block - Rear Body.
    • If the test lamp illuminates 
  5. Ignition OFF, connect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  6. Connect a test lamp between the appropriate trailer tail lamp control circuit listed below at the W8 Blunt Cut Trailer Provision and ground, ignition ON.
    • Left trailer tail lamp control (5184 BN/GY)
    • Right trailer tail lamp control (5185 GY)
  7. Verify the test lamp turns ON and OFF when commanding the appropriate Trailer Tail Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module.
    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, replace the K68 Trailer Lighting Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K68 Trailer Lighting Control Module.
    • If the test lamp turns ON and OFF 
  8. Test or replace the W8 Blunt Cut Trailer Provision.

Trailer Turn Signal Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  2. Test for less than 5 Ω between the ground circuit terminal 1 X2 and ground.
    • If 5 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 5 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
    • X1 terminal 13
    • X2 terminal 3
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the appropriate harness connector at the X53A Fuse Block - Rear Body.
    2. Test for infinite resistance between the B+ circuit terminal 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, replace the X53A Fuse Block - Rear Body.
    • If the test lamp illuminates 
  5. Ignition OFF, connect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  6. Connect a test lamp between the appropriate trailer turn signal lamp control circuit listed below at the W8 Blunt Cut Trailer Provision and ground, ignition ON.
    • Left trailer turn signal lamp control (5186 BU/WH)
    • Right trailer turn signal lamp control (5187 YE/GY)
  7. Verify the test lamp turns ON and OFF when commanding the appropriate Trailer Turn Signal Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module.
    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, replace the K68 Trailer Lighting Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K68 Trailer Lighting Control Module.
    • If the test lamp turns ON and OFF 
  8. Test or replace the W8 Blunt Cut Trailer Provision.

Trailer Stop Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  2. Test for less than 5 Ω between the ground circuit terminal 1 X2 and ground.
    • If 5 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 5 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
    • X1 terminal 13
    • X2 terminal 3
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the appropriate harness connector at the X53A Fuse Block - Rear Body.
    2. Test for infinite resistance between the B+ circuit terminal 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, replace the X53A Fuse Block - Rear Body.
    • If the test lamp illuminates 
  5. Ignition OFF, connect the X1 and X2 harness connectors at the K68 Trailer Lighting Control Module.
  6. Connect a test lamp between the trailer stop lamp control circuit (5188 BN/YE) at the W8 Blunt Cut Trailer Provision and ground, ignition ON.
  7. Verify the test lamp turns ON and OFF when commanding the Trailer Brake Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module.
    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, replace the K68 Trailer Lighting Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the K68 Trailer Lighting Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K68 Trailer Lighting Control Module.
    • If the test lamp turns ON and OFF 
  8. Test or replace the W8 Blunt Cut Trailer Provision.
scientia non olet · About LEMON Manuals