GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B2470

Circuit Description

The underhood fuse block provides ignition 1 voltage to the DRL relay coil. The Body Control Module (BCM) provides ground to the DRL relay in control circuit. The BCM monitors the voltage in the DRL relay control circuit every second.

Conditions for Running the DTC

A short to ground is tested under the following conditions:

    • The ignition switch is in the ON position.
    • The DRL relay is de-energized.

A short to battery will be tested under either of the following conditions:

    • The ignition switch is in the OFF position.
    • The ignition switch is in the ON position, and the DRL relay is energized.

Conditions for Setting the DTC

One of the following conditions will cause the DTC to set:

    • The DRL relay is de-energized, and the BCM detects that the voltage in the control circuit of the DRL relay is low for 2 seconds.
    • The DRL relay is energized, and the BCM detects that the control circuit of the DRL relay is high for 2 seconds.

Action Taken When the DTC Sets

The BCM turns OFF the DRL relay output, until the condition for setting the DTC is no longer present.

Conditions for Clearing the DTC

The DTC will clear when the following conditions are met:

    • The BCM detects that the voltage in the control circuit of the DRL relay is no longer low for 2 seconds.
    • The BCM detects that the control circuit of the DRL relay is no longer high for 2 seconds.

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. Tests for voltage at the coil side of the DRL relay. The IGN 1 fuse supplies power to the coil side of the DRL relay.

    3.

  3. Verifies that the Body Control Module (BCM) is providing ground to the DRL relay.

    4.

  4. Tests if ground is constantly being applied to the DRL relay.

Step

Action

Yes

No

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

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the 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. Turn OFF the ignition.
  2. Disconnect the DRL relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 1 voltage circuit of the DRL relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4

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

Does the test lamp turn ON and OFF 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 short to voltage or an open. 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

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 13

Go to Step 9

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 13

Go to Step 11

9

Inspect for poor connections at the harness connector of the Body Control Module (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

Repair an open or short to ground in the ignition 1 voltage circuit of the DRL relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

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

Did you complete the replacement?

Go to Step 13

--

12

Replace the 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