GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 DTC 🢒 DTC B2473

Circuit Description

The rear fuse block supplies battery positive voltage to the HIGH/LOW BEAM HEADLAMP relay coil. The Body Control Module (BCM) provides ground to the HIGH/LOW BEAM HEADLAMP relay in the control circuit. The BCM monitors the voltage in the HIGH/LOW BEAM HEADLAMP relay control circuit every second.

Conditions for Running the DTC

A short to ground in the HIGH/LOW BEAM HEADLAMP relay control circuit will be tested when the following conditions are met:

    • The ignition is ON.
    • The HIGH/LOW BEAM HEADLAMP relay is de-energized.

A short to battery positive voltage in the HIGH/LOW BEAM HEADLAMP relay control circuit will be tested when the following conditions are met:

    • The ignition is ON.
    • The HIGH/LOW BEAM HEADLAMP relay is energized.

Conditions for Setting the DTC

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

    • The HIGH/LOW BEAM HEADLAMP relay is de-energized, and the BCM detects that the voltage in the control circuit of the HIGH/LOW BEAM HEADLAMP relay is low for at least 2 seconds.
    • The HIGH/LOW BEAM HEADLAMP relay is energized, and the BCM detects that the control circuit of the HIGH/LOW BEAM HEADLAMP relay is high for at least 2 seconds.

Action Taken When the DTC Sets

The BCM turns OFF the HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP relay is no longer low for at least 2 seconds.
    • The BCM detects that the control circuit of the HIGH/LOW BEAM HEADLAMP relay is no longer high for at least 2 seconds.

Test Description

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

  1. Listen for an audible click when the HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP relay. The RADIO/PHONE fuse supplies power to the coil side of the HIGH/LOW BEAM HEADLAMP relay.

    3.

  3. Verifies that the BCM is providing ground to the HIGH/LOW BEAM HEADLAMP relay.

    4.

  4. Tests if ground is constantly being applied to the HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP relay ON and OFF.

Does the HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the battery positive voltage circuit of the HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP relay and the battery positive voltage circuit of the HIGH/LOW BEAM HEADLAMP relay coil.
  2. With a scan tool, command the HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP relay coil 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 HIGH/LOW BEAM HEADLAMP 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 HIGH/LOW BEAM HEADLAMP 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 battery positive voltage circuit of the HIGH/LOW BEAM HEADLAMP relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the HIGH/LOW BEAM HEADLAMP 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