GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Equinox 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC B2603

Circuit Description

The daytime running lights (DRL) relay is controlled by the body control module (BCM). Battery positive voltage is applied to the relay coil at all times. The BCM grounds the DRL relay control circuit in order to turn ON the DRL relay.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2603 Daytime Running Lamp Circuit High

Conditions for Running the DTC

The ignition switch is in the RUN position.

Conditions for Setting the DTC

All of the following conditions must be met:

    • The BCM is commanding the DRL relay ON.
    • The DRL relay control circuit is shorted to voltage.

Action Taken When the DTC Sets

The BCM disables the DRL relay control as long as the malfunction is present.

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

Diagnostic Aids
    • The park brake must not be set and the transaxle must be in gear for the DRL to operate properly.
    • If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Step

Action

Yes

No

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

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 lights (DRL) relay ON and OFF.

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

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3
  1. Disconnect the daytime running lights (DRL) relay.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the control 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 5

4
  1. Leave the test lamp connected.
  2. Turn OFF the ignition.
  3. Disconnect the body control module (BCM).
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 5

Go to Step 6

5

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 10

Go to Step 8

6

Inspect for poor connections at the harness connector of the body control 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 10

Go to Step 9

7

Repair a short to voltage in the DRL relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 10

--

8

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

Did you complete the replacement?

Go to Step 10

--

9

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 10

--

10
  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 3

System OK