Buick Regal: Headlamps Malfunction

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

1. Headlamps Malfunction - Low Beam
2. Headlamps Malfunction - High Beam
3. Headlamp Switch Malfunction
4. Turn Signal/Multifunction Switch Malfunction
5. Automatic High Beam Select Switch Malfunction

Circuit/System Description

Low Beam Headlamps (with T4A)

For headlamp operation, the body control module (BCM) monitors three signal circuits from the headlamp switch. When the headlamp switch is in the AUTO position, the three signal circuits are unaffected (open) and the BCM relies on the ambient light sensor input to turn the headlamps and daytime running lamps ON and OFF. When the headlamp switch is placed in the OFF position, the headlamp switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the headlamp switch in the PARK LAMPS position, the headlamp switch park lamps ON signal circuit is grounded, indicating that the park lamps have been requested.

When the headlamp switch is in the HEADLAMP position, both the headlamp switch park lamps ON signal circuit and the headlamp switch headlamps ON signal circuit are grounded. The BCM responds by commanding the park lamps and low beam headlamps ON. With the headlamp switch in the HEADLAMP or AUTO position, the BCM responds by applying battery positive voltage to the left and right low beam headlamp control circuits illuminating the low beam headlamps.

Low Beam Headlamps (with T4L)

For headlamp operation, the body control module (BCM) monitors three signal circuits from the headlamp switch. When the headlamp switch is in the AUTO position, the three signal circuits are unaffected (open) and the BCM relies on the ambient light sensor input to turn the headlamps and daytime running lamps ON and OFF. When the headlamp switch is placed in the OFF position, the headlamp switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the headlamp switch in the PARK LAMPS position, the headlamp switch park lamps ON signal circuit is grounded, indicating that the park lamps have been requested.

When the headlamp switch is in the HEADLAMP position, both the headlamp switch park lamps ON signal circuit and the headlamp switch headlamps ON signal circuit are grounded. The BCM responds to the low beam request by applying ground to the left and right low beam relay control circuits which energizes the left and right low beam relays. With the low beam relays energized, the switch contacts close allowing battery voltage to flow through the left and right low beam fuses. Battery voltage is then applied from the low beam fuses, through the low beam control circuits to the left and right headlamp/cornering lamp control modules located in each headlamp assembly. The left and right headlamp/cornering lamp control modules respond by illuminating the low beam LED headlamps.

High Beam Headlamps (with T4A)

The high beam and flash to pass functions are contained within the turn signal/multifunction switch. The BCM provides the turn signal/multifunction switch with two signal circuits, the high beam signal circuit and the flash to pass signal circuit. When the low beam headlamps are ON and the turn signal/multifunction switch is placed in the high beam position, ground is applied to the BCM through the high beam signal circuit. The BCM responds to the high beam request by applying ground to the high beam relay control circuit which energizes the high beam relay. With the high beam relay energized, the switch contacts close allowing battery voltage to flow through the left and right high beam fuses to the high beam control circuits illuminating the left and right high beam headlamps.

High Beam Headlamps (with T4L)

The high beam and flash to pass functions are contained within the turn signal/multifunction switch. The body control module (BCM) provides the turn signal/multifunction switch with two signal circuits, the high beam signal circuit and flash to pass signal circuit. When the low beam headlamps are ON and the turn signal/multifunction switch is placed in the high beam position, ground is applied to the BCM through the high beam signal circuit. The BCM responds to the high beam request by sending a message via serial data to the headlamp control module. The headlamp control module responds to the high beam request by communicating via serial data with the left and right headlamp/cornering lamp control modules located in each headlamp assembly. The left and right headlamp/cornering lamp control modules respond by illuminating there respective high beam LEDs.

Reference Information

Schematic Reference

• Headlights/Daytime Running Lights (DRL) Wiring Schematics
• Body Control System Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON.

2. Verify the scan tool Headlamps On Switch parameter changes between Active and Inactive while commanding the headlamp ON and OFF with the headlamp switch.

• If the parameter does not change

Refer to Circuit/System Testing - Headlamp Switch Malfunction.

• Go to next step: If the parameter changes

3. Verify the scan tool Automatic Headlamps Disable Switch parameter changes between Active and Inactive while commanding the automatic lamp control ON and OFF with the headlamp switch.

• If the parameter does not change

Refer to Circuit/System Testing - Headlamp Switch Malfunction.

• Go to next step: If the parameter changes

4. Verify the scan tool Headlamps Flash Switch parameter changes between Active and Inactive while commanding the flash to pass ON and OFF with the turn signal/multifunction switch.

• If the parameter does not change

Refer to Circuit/System Testing - Turn Signal/Multifunction Switch Malfunction.

• Go to next step: If the parameter changes

5. Verify the scan tool High Beam Select Switch parameter changes between Active and Inactive while commanding the high beams ON and OFF with the turn signal/multifunction switch.

• If the parameter does not change

Refer to Circuit/System Testing - Turn Signal/Multifunction Switch Malfunction.

• Go to next step: If the parameter changes

6. Verify the left low beam turns ON and OFF when commanding the Left Headlamp Low Beam ON and OFF with a scan tool.

• If the left low beam does not turn ON and OFF

Refer to Circuit/System Testing - Headlamps Malfunction - Low Beam.

• Go to next step: If the left low beam turns ON and OFF

7. Verify the right low beam turns ON and OFF when commanding the Right Headlamp Low Beam ON and OFF with a scan tool.

• If the right low beam does not turn ON and OFF

Refer to Circuit/System Testing - Headlamps Malfunction - Low Beam.

• Go to next step: If the right low beam turns ON and OFF

8. Low beam headlamps ON, verify the high beams turn ON and OFF when commanding the High Beams ON and OFF with the S78 Turn Signal/Multifunction Switch.

• If the high beams do not turn ON and OFF

Refer to Circuit/System Testing - Headlamps Malfunction - High Beam.

• Go to next step: If the high beams turn ON and OFF

9. Verify the high beam indicator on the instrument cluster turns ON and OFF while commanding the All Indicators ON and OFF with a scan tool.

• If the high beam indicator does not turn ON and OFF

Refer to Circuit/System Testing - High Beam Indicator Malfunction.

• Go to next step: If the high beam indicator turns ON and OFF

10. (TQ5/UVG only), verify the automatic high beam control indicator on the instrument cluster turns ON and OFF while commanding the automatic high beam control ON and OFF with the automatic high beam control switch located on the Turn Signal/Multifunction switch.

• If the automatic high beam control indicator does not turn ON and OFF

Refer to Circuit/System Testing - Automatic High Beam Select Switch Malfunction.

• Go to next step: If the automatic high beam control indicator turns ON and OFF

11. All OK.

Circuit/System Testing

Headlamp Switch Malfunction

1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close drivers door, 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 10 Ω between the ground circuit terminal 8 and ground.

• If 10 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.

• Go to next step: If less than 10 Ω

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 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.

• Go to next step: If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 3 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 1 V between the signal circuit terminal 3 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: 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 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.

• Go to next step: If Inactive

8. Install a 3 A fused jumper wire between the signal circuit terminal 5 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 1 V between the signal circuit terminal 5 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: 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 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

11. Install a 3 A fused jumper wire between the signal circuit terminal 1 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 1 V between the signal circuit terminal 1 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: 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, open and close drivers door, 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 10 Ω between the ground circuit terminal 3 and ground.

• If 10 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.

• Go to next step: If less than 10 Ω

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 7 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 7 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 1 V between the signal circuit terminal 7 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: 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 6 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

8. Install a 3 A fused jumper wire between the signal circuit terminal 6 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 1 V between the signal circuit terminal 6 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

10. Test or replace the S78 Turn Signal/Multifunction Switch.

Automatic High Beam Select Switch Malfunction (with TQ5/UVG)

1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close drivers door, 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 10 Ω between the ground circuit terminal 3 and ground.

• If 10 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.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Verify the automatic high beam control indicator on the instrument cluster is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the X2 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.

• Go to next step: If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground.

6. Verify the automatic high beam control indicator on the instrument cluster is Active.

• If not Active

1. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 4 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

7. Test or replace the S78 Turn Signal/Multifunction Switch.

Headlamps Malfunction - Low Beam (with T4A)

1. Ignition OFF, exterior lamps OFF, remove the appropriate E4 Headlamp - Low Beam bulb. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 5 Ω between the ground circuit at the socket terminal 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.

• Go to next step: If less than 5 Ω

3. Connect a test lamp between the control circuit at the socket terminal and ground, ignition ON.

4. Verify the test lamp turns ON and OFF when commanding the appropriate Headlamp Low Beam 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 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, 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 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 K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

5. Test or replace the E4 Headlamp - Low Beam.

Headlamps Malfunction - Low Beam (with T4L)

1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.

NOTE: The test lamp in the following step will illuminate at LOW intensity.

This is normal circuit operation and does not indicate a circuit malfunction.

2. Verify a test lamp illuminates between the appropriate control circuit terminal listed below and ground.

• Terminal 13 - left low beam
• Terminal 22 - right low beam
• If the test lamp does not illuminate

1. Ignition OFF, disconnect the X1 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.
   • 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, replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

3. Ignition OFF, connect a 3 A fused jumper between the appropriate control circuit terminal listed below and ground.

• Terminal 13 - left low beam
• Terminal 22 - right low beam

4. Remove the appropriate low beam fuse listed below at the X50A Fuse Block - Underhood, ignition ON.

• Fuse F59UA - left low beam
• Fuse F69UA - right low beam

5. Verify a test lamp illuminates between the low beam fuse 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 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 X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

6. Ignition OFF, connect the X5 harness connector at the K9 Body Control Module.

7. Install the low beam fuse 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 10 Ω between the ground circuit terminal 1 and ground.

• If 10 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.

• Go to next step: If less than 10 Ω

10. Connect a test lamp between the control circuit terminal 3 and ground, ignition ON.

11. Verify the test lamp turns ON and OFF when commanding the appropriate Headlamp Low Beam ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X5 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.
   • 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, replace the K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the X5 harness connector at the X50A Fuse Block - Underhood, 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 K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

12. Ignition OFF, connect the harness connector at the E13 Headlamp Assembly.

13. Disconnect the appropriate K189 Headlamp/Cornering Lamp Control Module. It may take up to 2 min for all vehicle systems to power down.

14. Test for less than 10 Ω between each ground circuit terminal listed below at the E13 Headlamp Assembly and ground.

• Terminal 2 X1
• Terminal 6 X1
• Terminal 33 X2
• If 10 Ω or greater

Replace the E13 Headlamp Assembly.

• Go to next step: If less than 10 Ω

15. Ignition ON, low beam headlamps ON.

16. Verify a test lamp illuminates between the B+ circuit terminal 1 at the E13 Headlamp Assembly and ground.

• If the test lamp does not illuminate

Replace the E13 Headlamp Assembly.

• Go to next step: If the test lamp illuminates

17. Replace the K189 Headlamp/Cornering Lamp Control Module.

Headlamps Malfunction - High Beam (with T4A)

1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.

NOTE: The test lamp in the following step will illuminate at LOW intensity.

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 X1 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.
   • 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, replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

3. Ignition OFF, connect a 3A fused jumper between the control circuit terminal 18 and ground.

4. Remove the left high beam fuse (F70UA) at the X50A Fuse Block - Underhood, ignition ON.

5. Verify a test lamp illuminates between the high beam fuse (F70UA) 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 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 X50A Fuse Block - Underhood.

• Go to next step: 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 (F70UA) at the X50A Fuse Block - Underhood.

8. Ignition OFF, exterior lamps OFF, remove the appropriate E4 Headlamp - High Beam. It may take up to 2 min for all vehicle systems to power down.

9. Test for less than 10 Ω between the ground circuit at the socket terminal and ground.

• If 10 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.

• Go to next step: If less than 10 Ω

10. Connect a test lamp between the control circuit at the socket terminal and ground, ignition ON, low beam headlamps ON.

11. Verify the test lamp turns ON and OFF when commanding the High Beams ON and OFF with the S78 Turn Signal/Multifunction Switch.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X5 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.
   • 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, replace the K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the X5 harness connector at the X50A Fuse Block - Underhood, 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 K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

12. Test or replace the E4 Headlamp - High Beam.

High Beam Indicator Malfunction

1. Ignition ON.

2. Verify the high beam indicator turns ON and OFF when commanding the Instrument Cluster All Indicators ON and OFF with a scan tool.

• If the high beam indicator is always OFF or remains ON

Replace the P16 Instrument Cluster.

• Go to next step: If the high beam indicator turns ON and OFF

3. Replace the K9 Body Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Switch Replacement
• Turn Signal Switch Replacement
• Headlamp Bulb Replacement - Left Side (High Beam) Headlamp Bulb Replacement - Left Side (Low Beam)
• Headlamp Bulb Replacement - Right Side (High Beam) Headlamp Bulb Replacement - Right Side (Low Beam)
• Engine Wiring Harness Fuse Block Bracket Replacement
• Control Module References for BCM, Headlamp Control module, Headlamp/Cornering Lamp Control module, or Instrument Cluster replacement, programming, and setup

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