Buick Regal: DTC B259C or B259D

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.

DTC Descriptors

DTC B259C 03

Left High Beam Power Circuit Low Voltage

DTC B259C 07

Left High Beam Power Circuit High Voltage

DTC B259D 03

Right High Beam Power Circuit Low Voltage

DTC B259D 07

Left High Beam Power Circuit High Voltage

Diagnostic Fault Information

1. Headlamps Malfunction
2. Headlamp Leveling Malfunction

Circuit/System Description

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 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 sending a message via serial data to the headlamp control module. The headlamp control module responds to the high beam request by sending a serial data message 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 their respective high beam LEDs.

Conditions for Running the DTC

• Battery voltage must be between 9 - 16 V.
• High beam headlamps ON.

Conditions for Setting the DTC

DTC B259C 03

The headlamp control module detects a low voltage condition in the headlamp/cornering lamp control module - left B+ circuit.

DTC B259C 07

The headlamp control module detects a high voltage condition in the headlamp/cornering lamp control module - left B+ circuit.

DTC B259D 03

The headlamp control module detects a low voltage condition in the headlamp/cornering lamp control module - right B+ circuit.

DTC B259D 07

The headlamp control module detects a high voltage condition in the headlamp/cornering lamp control module - right B+ circuit.

Actions Taken When the DTC Sets

• One or more of the high beam LEDs are inoperative.
• The driver information center will display "Advanced Front Lighting System Fault" and "Headlamp Leveling Malfunction".

Conditions for Clearing the DTC

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

The following control modules located on each headlamp assembly are serviceable.

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

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) 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 Testing

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 High 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. Replace the E13 Headlamp Assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Replacement
• Engine Wiring Harness Fuse Block Bracket Replacement
• Control Module References for BCM or Headlamp/Cornering Lamp Control Module replacement, programming, and setup

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