LEMON Manuals: Even more car manuals for everyone
Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Interior/Illumination Lights >> Lighting System - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> Headlamps Malfunction >> Circuit/System Testing

Circuit/System Testing

Headlamp Switch Malfunction

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S30 Headlamp Switch. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15Ω between the ground circuit terminal 6 and ground.
    • If 15Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 15Ω 
  3. Ignition ON.
  4. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 5 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 3A fused jumper wire between the signal circuit terminal 5 and ground.
  6. Verify the scan tool Automatic Headlamps Disable Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the signal circuit terminal 5 and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V
    3. Test for less than 2Ω in the signal circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If Active 
  7. Verify the scan tool Park Lamps Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 3 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 
  8. Install a 3A fused jumper wire between the signal circuit terminal 3 and ground.
  9. Verify the scan tool Park Lamps Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the signal circuit terminal 3 and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V
    3. Test for less than 2Ω in the signal circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If Active 
  10. Verify the scan tool Headlamps On Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 4 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 
  11. Install a 3A fused jumper wire between the signal circuit terminal 4 and ground.
  12. Verify the scan tool Headlamps On Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the signal circuit terminal 4 and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V
    3. Test for less than 2Ω in the signal circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If Active 
  13. Test or replace the S30 Headlamp Switch.

Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S78 turn Signal/Multifunction Switch. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15Ω between the ground circuit terminal 3 and ground.
    • If 15Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 15Ω 
  3. Ignition ON.
  4. Verify the scan tool High Beam Select Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X3 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 2 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 3A fused jumper wire between the signal circuit terminal 2 and ground.
  6. Verify the scan tool High Beam Select Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X3 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the signal circuit terminal 2 and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V
    3. Test for less than 2Ω in the signal circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If Active 
  7. Verify the scan tool Headlamps Flash Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X3 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 4 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 
  8. Install a 3A fused jumper wire between the signal circuit terminal 4 and ground.
  9. Verify the scan tool Headlamps Flash Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X3 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the signal circuit terminal 4 and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V
    3. Test for less than 2Ω in the signal circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If Active 
  10. Test or replace the S78 turn Signal/Multifunction Switch.

Headlamps Malfunction - Low Beam (with T4A)

  1. Ignition OFF, disconnect the appropriate KR49 Headlamp Low Beam Relay, ignition ON.
  2. Connect a test lamp between the control circuit terminal 30 and ground, ignition ON.
  3. Verify the test lamp turns ON and OFF when commanding the appropriate Low Beam Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the control 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 2Ω in the control circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the control circuit terminal and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V, replace the K9 body Control Module.
    • If the test lamp turns ON and OFF 
  4. Ignition OFF, exterior lamps OFF, connect the KR49 Headlamp Low Beam Relay.
  5. Remove the appropriate E4 Headlamp - Low Beam bulb. It may take up to 2 min for all vehicle systems to power down.
  6. Test for less than 10Ω between the ground circuit at the socket terminal and ground.
    • If 10Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 10Ω 
  7. Connect a test lamp between the control circuit at the socket terminal and ground, ignition ON.
  8. Verify the test lamp turns ON and OFF when commanding the appropriate Low Beam Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the appropriate KR49 Headlamp Low Beam Relay.
    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 2Ω in the control circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the KR49 Headlamp Low Beam Relay.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the appropriate KR49 Headlamp Low Beam Relay, ignition ON.
    2. Test for less than 1V between the control circuit terminal and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V, replace the KR49 Headlamp Low Beam Relay.
    • If the test lamp turns ON and OFF 
  9. Test or replace the E4 Headlamp - Low Beam.

Headlamps Malfunction - Low Beam (with T4F)

  1. Ignition OFF, disconnect the KR49L Headlamp Low Beam Relay, ignition ON
  2. Verify a test lamp illuminates between the B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block - Underhood.

    • If the test lamp illuminates 
  3. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block - Underhood.

    • If the test lamp illuminates 
  4. Connect a test lamp between the control circuit terminal 85 and B+, ignition ON.
  5. Verify the test lamp turns ON and OFF when commanding the Low Beam Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X5 harness connector at the K9 body Control Module, ignition ON.
    2. Test for less than 1V between the control circuit terminal and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V
    3. Ignition OFF.
    4. Test for less than 2Ω in the control circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X5 harness connector at the K9 body Control Module.
    2. Test for infinite resistance between the control circuit terminal 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 the test lamp turns ON and OFF 
  6. Ignition OFF, exterior lamps OFF, connect the KR49L Headlamp Low Beam Relay.
  7. Disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  8. Test for less than 10Ω between the ground circuit terminal 10 and ground.
    • If 10Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 10Ω 
  9. Connect a test lamp between the control circuit terminal 3 and ground, ignition ON.
  10. Verify the test lamp turns ON and OFF when commanding the Low Beam 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 X50A Fuse Block - Underhood.
    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 2Ω in the control circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the KR49L Headlamp Low Beam Relay.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood, ignition ON.
    2. Test for less than 1V between the control circuit terminal and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V, replace the KR49L Headlamp Low Beam Relay.
    • If the test lamp turns ON and OFF 
  11. Ignition OFF, replace the appropriate T7 Headlamp Ballast.
  12. Ignition ON, verify the appropriate low beam headlamp illuminates when commanded ON with the headlamp switch.
    • If the low beam headlamp does not illuminate 
    1. Replace the appropriate E4 Headlamp - Low Beam bulb.
    • If the low beam headlamp illuminates 
  13. All OK.

Headlamps Malfunction - High Beam

  1. Ignition OFF, disconnect the X5 harness connector at the K9 body Control Module, ignition ON.
  2. Verify a test lamp illuminates between the control circuit terminal 18 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
    2. Test for infinite resistance between the control 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 2Ω in the control circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the X50A Fuse Block - Underhood.
    • If the test lamp illuminates 
  3. Ignition OFF, connect a 3 A fused jumper between the control circuit terminal 18 and ground.
  4. Remove the left high beam fuse (F38UA) at the X50A Fuse Block - Underhood, ignition ON.
  5. Verify a test lamp illuminates between the left high beam fuse (F38UA) B+ switch control terminal and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood, ignition ON.
    2. Test for less than 1V between the control circuit terminal and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V, replace the X50A Fuse Block - Underhood.
    • If the test lamp illuminates 
  6. Ignition OFF, connect the X5 harness connector at the K9 body Control Module.
  7. Install the left high beam fuse (F38UA) at the X50A Fuse Block - Underhood.
  8. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  9. Test for less than 10Ω between the ground circuit terminal 1 and ground.
    • If 10Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 10Ω 
  10. Connect a test lamp between the control circuit terminal 2 and ground, ignition ON.
  11. Verify the test lamp turns ON and OFF when commanding the High Beams ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood.
    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 2Ω in the control circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the K9 body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood, ignition ON.
    2. Test for less than 1V between the control circuit terminal and ground.
      • If 1V or greater, repair the short to voltage on the circuit.
      • If less than 1V, replace the K9 body Control Module.
    • If the test lamp turns ON and OFF 
  12. Test or replace the M28 High Beam Solenoid Actuator.

High Beam Indicator Malfunction

  1. Ignition ON.
  2. Verify the high beam indicator turns ON and OFF when commanding the Instrument Cluster All Indicators Test ON and OFF with a scan tool.
    • If the high beam indicator is always OFF or remains ON 

      Replace the P16 Instrument Cluster.

    • If the high beam indicator turns ON and OFF 
  3. Replace the K9 body Control Module.
scientia non olet · About LEMON Manuals