GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 DTC 🢒 DTC B2471

Circuit Description

The INT LPS fuse in the underhood fuse block supplies battery positive voltage to the COURTESY relay coil. The Body Control Module (BCM) provides ground to the COURTESY relay in the control circuit. The BCM monitors the voltage in the COURTESY relay control circuit every second.

Conditions for Running the DTC

A short to ground in the control circuit of the COURTESY relay will be tested when the following conditions are met:

    • Ignition ON, with the COURTESY relay de-energized, and the Inadvertent Power relay energized.
    • DTC B1971 is not present.

A short to battery positive voltage in the control circuit of the COURTESY relay will be tested when the following conditions are met:

    • Ignition ON, with the COURTESY relay energized, and the Inadvertent Power relay energized.
    • DTC B1971 is not present.

Conditions for Setting the DTC

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

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

Action Taken When the DTC Sets

The BCM turns OFF the COURTESY 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 COURTESY relay is no longer low for at least 2 seconds.
    • The BCM detects that the control circuit of the COURTESY relay is no longer high for at least 2 seconds.

Test Description

  1. Listen for an audible click when the COURTESY LP 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 COURTESY LP relay. The INT LPS fuse supplies power to the coil side of the COURTESY LP relay.

    3.

  3. Verifies that the BCM is providing ground to the COURTESY LP relay.

    4.

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

Step

Action

Yes

No

Schematic Reference: Interior Lights 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 COURTESY relay ON and OFF.

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

Did you complete the repair?

Go to Step 13

--

11

Replace the COURTESY 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