Buick Regal: DTC B2600 or B2605
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 B2600 01
Left Daytime Running Lamps Control Circuit short to Battery
DTC B2600 02
Left Daytime Running Lamps Control Circuit Short to Ground
DTC B2600 04
Left Daytime Running Lamps Control Circuit Open
DTC B2605 01
Right Daytime Running Lamps Control Circuit short to Battery
DTC B2605 02
Right Daytime Running Lamps Control Circuit Short to Ground
DTC B2605 04
Right Daytime Running Lamps Control Circuit Open
Diagnostic Fault Information
1. Headlamps Malfunction
2. 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 5-volt 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 volts. The BCM monitors the ambient light sensor signal circuit to determine
if outside lighting
conditions are correct for either daytime running lights (DRL) or automatic
headlamp system control
when the headlamp switch is in the AUTO position. In daylight conditions, the
BCM will command the
DRLs. Any function or condition that turns on the headlamps will cancel DRL
operation.
Conditions for Running the DTC
- Battery voltage must be between 9-16 V.
- Headlamp switch in AUTO position.
Conditions for Setting the DTC
DTC B2600 01
The BCM detects a short to voltage in the left DRL control circuit.
DTC B2600 02
The BCM detects a short to ground in the left DRL control circuit.
DTC B2600 04
The BCM detects an open/high resistance in the left DRL control circuit.
DTC B2605 01
The BCM detects a short to voltage in the right DRL control circuit.
DTC B2605 02
The BCM detects a short to ground in the right DRL control circuit.
DTC B2605 04
The BCM detects an open/high resistance in the right DRL control circuit.
Actions Taken When the DTC Sets
- When DTC B2600 sets, the left DRL will be inoperative.
- When DTC B2605 sets, the right DRL will be inoperative.
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.
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, exterior lamps OFF, disconnect the harness connector at the
appropriate E13
headlamp.
2. Test for less than 5 Ω between the ground circuit terminal 1 and ground.
- Ignition OFF.
- 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 terminal 4 and ground,
ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the appropriate Front
Park
Lamp/Daytime Running Lamp ON and OFF with a scan tool.
- If the test lamp is always OFF
- Ignition OFF, disconnect the X4 harness connector at the K9 body control
module.
- 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
- 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
- Ignition OFF, disconnect the X4 harness connector at the K9 body control
module, ignition
ON.
- 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 E13 headlamp.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Headlamp Replacement
- Control Module References for BCM replacement, programming, and setup
READ NEXT:
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.
Diag
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.
Diag
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.
Diag
SEE MORE:
WARNING: If a service procedure indicates that a module is to be
replaced, a new
production unit MUST be ordered from the GM Parts Catalog or certified
supplier. Using a module that has been reset by a 3rd party company is strictly
prohibited. Not using a new production unit may result in improper
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
D