GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Classic 🢒 Body 🢒 Lighting Systems 🢒 DTC B2601

Circuit Description

The daytime running lamps (DRL) relay is controlled by the body control module (BCM). Battery positive voltage is applied to the DRL relay coil at all times. The BCM grounds the DRL relay control circuit in order to turn ON the DRL relay. When the DRL relay control circuit becomes shorted to ground or the DRLs remain illuminated without being commanded ON by the BCM, DTC B2601 is set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2601 Daytime Running Lamp Control System Circuit Range/Performance

Conditions for Running the DTC
    • The ignition switch is in the ON position.
    • The headlamp switch is in the OFF position.
    • The transaxle is in PARK.

Conditions for Setting the DTC

All of the following conditions must be met:

    • The BCM is not commanding the DRL relay ON.
    • The headlamp feedback is present for 5 seconds.

Action Taken When the DTC Sets
    • The BCM disables the DRL relay control as long as the malfunction is present.
    • The SERVICE indicator illuminates.

Conditions for Clearing the DTC
    • The conditions for setting the DTC are no longer present.
    • A history DTC clears after 100 malfunction-free ignition cycles.
    • The BCM receives the clear code command from the scan tool.

Diagnostic Aids
    • If DTC B2602 is set along with DTC B2601, test the DRL relay control circuit between the BCM and the DRL relay for a short to ground.
    • The park brake must be unapplied and the transaxle must be in gear for the DRLs to operate properly.
    • Intermittent malfunctions are cumulative. When the malfunction exists for a total of 5 seconds, DTC B2601 is set.
    • If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. Listen for an audible click when the DRL relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.

    2.

  2. This step tests for voltage at the coil side of the DRL relay.

    3.

  3. This step verifies that the BCM is providing ground to the DRL relay.

    4.

  4. This step tests if ground is constantly being applied to the DRL relay.

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the daytime running lamps (DRL) relay ON and OFF.

Does the DRL relay turn ON and OFF with each command?

Go to Step 9

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the DRL relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side battery positive voltage circuit of the DRL relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 12

4

  1. Connect a test lamp between the control circuit of the DRL relay and the coil side battery positive voltage circuit of the DRL relay.
  2. With a scan tool, command the DRL relay ON and OFF .

Does the test lamp turn illuminate with each command?

Go to Step 8

Go to Step 5

5

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 6

6

Test the control circuit of the DRL relay for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 11

7

Test the control circuit of the DRL relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 11

8

Inspect for poor connections at the DRL relay. 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 15

Go to Step 13

9
  1. Disconnect both front headlamp connectors.
  2. Disconnect the headlamp switch connector.
  3. Disconnect the body control module (BCM) connectors.
  4. Turn the ignition switch to the ON position.
  5. Test the low beam control circuit between the front headlamps, BCM, and the headlamp switch for a short to battery voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 10

10

Test the high beam control circuit between the front headlamps, BCM, and the headlamp switch for a short to battery voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 15

Go to Step 11

11

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

Did you complete the replacement?

Go to Step 15

Go to Step 14

12

Repair the open in the coil side battery positive voltage circuit of the DRL relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

--

13

Replace the DRL relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 15

--

14

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming .

Did you complete the replacement?

Go to Step 15

--

15
  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