Buick Regal: DTC B260B or B260C

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 B260B 02

Left Daytime Running Lamp Relay Control Circuit Short to Ground

DTC B260B 04

Left Daytime Running Lamp Relay Control Circuit Open

DTC B260C 02

Right Daytime Running Lamp Relay Control Circuit Short to Ground

DTC B260C 04

Right Daytime Running Lamp Relay Control Circuit Open

Diagnostic Fault Information

1. Daytime Running Lamps Malfunction

Circuit/System Description

The ambient light sensor is used to monitor outside lighting conditions. The body control module (BCM) provides a low reference ground and 5 V reference signal to the ambient light sensor. Depending on outside lighting conditions, the ambient light sensor provides a voltage signal to the BCM that will vary between 0.2 and 4.9 V. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps or automatic headlamp system control when the headlamp switch is in the AUTO position. In daylight conditions, the BCM responds by applying battery voltage to the left and right daytime running lamp relay control circuits which energizes both daytime running lamp relays. With the daytime running lamp relays energized, the switch contacts close allowing battery voltage to flow to the daytime running lamp control circuits illuminating the left and right daytime running lamp.

Conditions for Running the DTC

• Battery voltage must be between 9 - 16 V.
• Engine ON.
• Headlamp switch in AUTO position.
• Ambient light is day.

Conditions for Setting the DTC

DTC B260B 02

The BCM detects a short to ground in the left daytime running lamp relay control circuit.

DTC B260B 04

The BCM detects an open/high resistance in the left daytime running lamp relay control circuit.

DTC B260C 02

The BCM detects a short to ground in the right daytime running lamp relay control circuit.

DTC B260C 04

The BCM detects an open/high resistance in the right daytime running lamp relay control circuit.

Actions Taken When the DTC Sets

The appropriate daytime running lamp is inoperative.

Conditions for Clearing the DTC

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

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

Circuit/System Testing

DTC B260B

1. Ignition OFF, disconnect the KR42L Daytime Running Lamp Relay - Left.

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.

• Go to next step: 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.

• Go to next step: 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 Left Daytime Running Lamp 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 1 V between the control 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. Ignition OFF.
4. 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 K9 Body Control Module.
2. Test for infinite resistance between the control 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.

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

6. Test or replace the KR42L Daytime Running Lamp Relay - Left.

DTC B260C

1. Ignition OFF, disconnect the KR42R Daytime Running Lamp Relay - Right.

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.

• Go to next step: 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.

• Go to next step: 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 Right Daytime Running Lamp 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 1 V between the control circuit terminal 15 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. Ignition OFF.
4. 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 K9 Body Control Module.
2. Test for infinite resistance between the control circuit terminal 15 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 the test lamp turns ON and OFF

6. Test or replace the KR42R Daytime Running Lamp Relay - Right.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
• Control Module References for BCM replacement, programming, and setup.

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