Buick Regal: Park, License, and/or Tail Lamps 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. Park, License, and/or Tail Lamps Malfunction
2. Headlamp Switch Malfunction

Circuit/System Description

When the headlamp switch is placed in the HEAD or PARK position, ground is applied to the park lamp switch ON signal circuit to the body control module (BCM). The BCM responds by applying voltage to the park lamps, tail lamps, and license lamps control circuits illuminating the park, tail, and license lamps.

Diagnostic Aids

When replacing a headlamp assembly, the following control modules located on each headlamp assembly are serviceable.

• K189L Headlamp/Cornering Lamp Control Module - Left
• K189R Headlamp/Cornering Lamp Control Module - Right
• K26L Headlamp Control Module - Left
• K26R Headlamp Control Module - Right

Reference Information

Schematic Reference

Exterior Lights 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 Park Lamp Switch parameter changes between Active and Inactive while commanding the park lamps 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 left park lamps turn ON and OFF when commanding the Left Park Lamps ON and OFF with a scan tool.

• If the left park lamps do not turn ON and OFF

Refer to Circuit/System Testing - Park Lamps Malfunction.

• Go to next step: If the left park lamps turn ON and OFF

4. Verify the right park lamps turn ON and OFF when commanding the Right Park Lamps ON and OFF with a scan tool.

• If the right park lamps do not turn ON and OFF

Refer to Circuit/System Testing - Park Lamps Malfunction.

• Go to next step: If the right park lamps turn ON and OFF

5. Verify the license plate lamps turn ON and OFF when commanding the License Plate Lamps ON and OFF with a scan tool.

• If the license plate lamps do not turn ON and OFF

Refer to Circuit/System Testing - License Plate Lamps Malfunction.

• Go to next step: If the license plate lamps turn ON and OFF

6. 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 15 Ω between the ground circuit terminal 8 and ground.

• If 15 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 15 Ω

3. Ignition ON.

4. 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

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

6. 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

7. Test or replace the S30 Headlamp Switch.

Park Lamps Malfunction

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.

• E13LA Headlamp Assembly - Left
• E13RA Headlamp Assembly - Right
• E2LF Side Market Lamp - Left Front
• E2RF Side Market Lamp - Right Front
• E42L Tail Lamp Assembly - Left
• E42R Tail Lamp Assembly - Right
• E43L Liftgate Tail Lamp Assembly - Left
• E43R Liftgate Tail Lamp Assembly - Right

2. Test for less than 10 Ω between the appropriate ground circuit terminal listed below and ground.

• E13LA Headlamp Assembly - Left terminal 1 (with T4L)
• E13RA Headlamp Assembly - Right terminal 1 (with T4L)
• E2LF Side Market Lamp - Left Front terminal 2
• E2RF Side Market Lamp - Right Front terminal 2
• E13LA Headlamp Assembly - Left terminal 2 (with T4A)
• E13RA Headlamp Assembly - Right terminal 2 (with T4A)
• E42L Tail Lamp Assembly - Left terminal 4
• E42R Tail Lamp Assembly - Right terminal 4
• E43L Liftgate Tail Lamp Assembly - Left terminal 4
• E43R Liftgate Tail Lamp Assembly - Right terminal 4
• 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. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.

• E13LA Headlamp Assembly - Left terminal 4
• E13RA Headlamp Assembly - Right terminal 4
• E2LF Side Market Lamp - Left Front terminal 1
• E2RF Side Market Lamp - Right Front terminal 1
• E42L Tail Lamp Assembly - Left terminal 1
• E42R Tail Lamp Assembly - Right terminal 1
• E43L Liftgate Tail Lamp Assembly - Left terminal 1
• E43R Liftgate Tail Lamp Assembly - Right terminal 1

4. Verify the test lamp turns ON and OFF when commanding the appropriate Park Lamps 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 park lamp.

License Plate Lamps Malfunction

1. Ignition OFF, exterior lamps OFF, disconnect the appropriate E7 License Plate Lamp. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between each 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

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 License Plate Lamps 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 appropriate E7 License Plate Lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Replacement
• Rear License Plate Lamp Replacement
• Rear Body Structure Stop Lamp Replacement (5-Door Hatchback 68) Rear Body Structure
• Stop Lamp Replacement (5-Door Wagon 35)
• Tail Lamp Replacement (5-Door Hatchback 68) Tail Lamp Replacement (5-Door Wagon 35)
• Control Module References for BCM replacement, programming, and setup

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