Buick Regal: Dome 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. Dome Lamps Malfunction
2. Dome Lamp Switch Malfunction

Circuit/System Description

The dome lamp switch has 3 positions: DOOR, OFF, and ON. The ON position provides a ground for continuous operation and the dome lamp will remain illuminated until the switch is placed in either the DOOR or OFF position. When in the DOOR position, the dome lamp operation is controlled by the body control module (BCM). When any door is opened, the door ajar switch contacts close and the BCM receives a door-open input. The BCM illuminates the dome lamp when any door is opened or a door lock/unlock request is activated with the key fob. After all doors have been closed, the dome lamp will remain illuminated approximately 3 seconds after the last door closes. When the driver places the dome lamp switch in the OFF position, the dome lamp will be disabled. In the event that the dome lamp were to remain illuminated for more than 10 minutes with the ignition switch in the OFF position and no doors opened, the BCM will deactivate the dome lamp control circuit to prevent total battery discharge.

Reference Information

Schematic Reference

• Interior Lights Wiring Schematics
• Power Distribution Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Interior 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 Door Ajar Sw. parameter changes between Active and Inactive while opening and closing each vehicle door.

• If the parameter does not change

Refer to Door Ajar Indicator Malfunction.

• Go to next step: If the parameter changes

3. Verify the scan tool Interior/Courtesy Lighting Master Switch parameter changes between Door, On, and Cancel while placing the dome lamp switch in the Door, On, and Cancel positions.

• If the parameter does not change

Refer to Circuit/System Testing - Dome Lamp Switch Malfunction.

• Go to next step: If the parameter changes

4. Verify the dome lamps turn ON and OFF while commanding the Courtesy Lamps ON and OFF with a scan tool.

• If the dome lamps do not turn ON and OFF

Refer to Circuit/System Testing - Dome Lamps Malfunction.

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

5. All OK.

Circuit/System Testing

Dome Lamp Switch Malfunction

1. Ignition OFF, all doors closed, all accessories OFF, open and close drivers door, disconnect the harness connector at the A98 Front Overhead Console Assembly. 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 5 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 Interior/Courtesy Lighting Master Switch parameter is Door.

• If Cancel

1. Ignition OFF, disconnect the X7 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 21 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 On

1. Ignition OFF, disconnect the X2 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 Door

5. Install a 3 A fused jumper wire between the signal circuit terminal 21 and ground.

6. Verify the scan tool Interior/Courtesy Lighting Master Switch parameter is Cancel.

• If not Cancel

1. Ignition OFF, disconnect the X7 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 21 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 Cancel

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

8. Verify the scan tool Interior/Courtesy Lighting Master Switch parameter is On.

• If not On

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 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 On

9. Test or replace the A98 Front Overhead Console Assembly.

Dome Lamps Malfunction

NOTE: Each lighting component may need to be disconnected to isolate a short to ground. Use the schematics to identify the following:

• Lighting components the vehicle is equipped with
• Each component's control and ground circuit terminals
• Component locations on the lighting control circuit

1. Ignition OFF, disconnect the harness connectors at the appropriate components listed below, ignition ON.

• A98 Front Overhead Console Assembly
• B177 Rain/Ambient Light Sensor Module (with CE1)
• E37R Dome/Reading Lamps - Rear (with C93)

2. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the F41DA fuse at the X51A Fuse Block - Instrument Panel.
2. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the F41DA fuse at the X51A Fuse Block - Instrument Panel.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the appropriate component listed below.
3. A98 Front Overhead Console Assembly
4. B177 Rain/Ambient Light Sensor Module (with CE1)
5. E37R Dome/Reading Lamps - Rear (with C93)

• Go to next step: If the test lamp illuminates

3. Ignition OFF, connect the harness connectors at the appropriate components listed below.

• A98 Front Overhead Console Assembly
• B177 Rain/Ambient Light Sensor Module (with CE1)
• E37R Dome/Reading Lamps - Rear (with C93)

4. Ignition OFF, all doors closed, all accessories OFF, open and close drivers door, disconnect the harness connector at the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.

• A98 Front Overhead Console Assembly
• E37H Dome/Reading Lamps - Left Roof Rail (with C3U)
• E37J Dome/Reading Lamps - Right Roof Rail (with C3U)
• E37R Dome/Reading Lamps - Rear (without C3U)
• E1AA Floor Accent Lamp - Left Front (with C93)
• E1AB Floor Accent Lamp - Right Front (with C93)

5. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.

• A98 Front Overhead Console Assembly terminal 5
• E37H Dome/Reading Lamps - Left Roof Rail terminal 3 (with C3U)
• E37J Dome/Reading Lamps - Right Roof Rail terminal 3 (with C3U)
• E37R Dome/Reading Lamps - Rear terminal 3 (without C3U)
• E1AA Floor Accent Lamp - Left Front terminal 2 (with C93)
• E1AB Floor Accent Lamp - Right Front terminal 2 (with C93)
• 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

6. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.

• A98 Front Overhead Console Assembly terminal 8
• E37H Dome/Reading Lamps - Left Roof Rail terminal 4 (with C3U)
• E37J Dome/Reading Lamps - Right Roof Rail terminal 4 (with C3U)
• E37R Dome/Reading Lamps - Rear terminal 2 (without C3U)
• E1AA Floor Accent Lamp - Left Front terminal 1 (with C93)
• E1AB Floor Accent Lamp - Right Front terminal 1 (with C93)

7. Verify the test lamp turns ON and OFF when commanding the Courtesy Lamps ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X7 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 X7 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

8. Test or replace the appropriate courtesy/dome Lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Center Reading Lamp Replacement (without Sunroof)
• Front Floor Flood Lamp Replacement
• Rear Seat Position Center Reading Lamp Replacement (with Sunroof)
• Roof Console Replacement
• Control Module References for BCM replacement, programming, and setup

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