GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 Savana 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B2600

Circuit Description

The body control module (BCM) signals the turn/hazard flasher module to illuminate the daytime running lamps (DRL) by grounding the DRL low control circuit. The DRL operates when the ignition switch is in the RUN position and the gear selector is not in the park position.

Conditions for Running the DTC

The battery voltage must be between 9.0-16.0 volts.

Conditions for Setting the DTC
    • When the BCM sends a DRL OFF command and the DRL low control circuit is shorted to ground.
    • When the BCM sends a DRL ON command and the DRL low control circuit is shorted to voltage or open.
    • When the Flasher fuse 15 in the underhood fuse block is open.
    • When the following circuits are shorted to ground:
       - Left rear stop/turn lamp supply voltage
       - Right rear stop/turn lamp supply voltage
       - Left DRL/turn supply voltage
       - Right DRL/turn supply voltage
       - Left turn signal indicator lamp supply voltage
       - Right turn signal indicator lamp supply voltage
       - Battery supply voltage from the underhood fuse block Flasher fuse
    • The instrument panel lamps dimming control circuit is shorted to ground.

Action Taken When the DTC Sets

The DRL will not operate or will remain always on.

Conditions for Clearing the MIL/DTC
    • This DTC will clear on current status after the condition for setting the fault is corrected.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • History and current DTCs can be cleared using a scan tool.

Diagnostic Aids
    • Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • A short to ground in the following circuits will cause the Flasher fuse to open.
       - Left rear stop/turn lamp supply voltage
       - Right rear stop/turn lamp supply voltage
       - Left DRL/turn supply voltage
       - Right DRL/turn supply voltage
       - Left turn signal indicator lamp supply voltage
       - Right turn signal indicator lamp supply voltage
       - Battery supply voltage from the underhood fuse block Flasher fuse
    • An open in the Flasher fuse will cause the DRL, turn signals and the hazard flashers to be inoperative.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step test determines if the problem exists in the DRL control/BCM or other circuitry.

    2.

  2. This step test determines if the problem exists in the wiring or the BCM.

    3.

  3. This step test determines if the problem exists in the wiring or the BCM.

    4.

  4. After replacement of the BCM you must calibrate the new module for proper operation.

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Lighting Systems Connector End Views or Body Control System Connector End Views in Body Control System

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Are the DRL, turn signals and the hazard flashers all inoperative?

Go to Step 3

Go to Step 7

3

Is the Flasher fuse in the under hood fuse block open?

Go to Step 6

Go to Step 4

4

Test the ground circuit of the turn/hazard flasher module for a high resistance or an open.

Did you find and correct the condition?

Go to Step 13

Go to Step 5

5

Test the battery positive voltage circuit of the turn/hazard flasher module for a high resistance or an open.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

6

Test the following circuits for a short to ground:

    • Left rear stop/turn lamp supply voltage
    • Right rear stop/turn lamp supply voltage
    • Left DRL/turn supply voltage
    • Right DRL/turn supply voltage
    • Left turn signal indicator lamp supply voltage
    • Right turn signal indicator lamp supply voltage

Did you find and correct the condition?

Go to Step 13

Go to Step 11

7

Test the DRL low control circuit for high resistance, an open, or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

8

Inspect for poor connections at the harness connector of the turn/hazard flasher module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

9

Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

10

Replace the turn/hazard flasher module. Refer to Hazard and Turn Signal Flasher Replacement .

Did you complete the replacement?

Go to Step 13

--

11

Repair the battery positive voltage circuit from the Flasher fuse in the under hood fuse block.

Did you complete the repair?

Go to Step 13

--

12

Important: Perform the setup procedure for the BCM.

Replace the body control module (BCM). Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 13

--

13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK