GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Corvette 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B0503

Circuit Description

The BCM provides control for the R DRL relay circuit. The BCM grounds the R DRL relay control circuit in order to energize the R DRL relay andturn ON the RF turn signal. This allows the RF turn signal to be used for DRL, UTD, and approach lighting functions. The BCM monitors the voltage levelon the R DRL relay control circuit. When the BCM commands the relay ON, the voltage level on the R DRL relay control circuit should be low. When the relay is OFF, the voltage on the R DRL relay control circuitshouldbe high. If the BCM detects a voltage level other than expected,a malfunctionis present and a DTC will set.

Conditions for Setting the DTC
    • The BCM detects a high voltage level (a short to battery positive voltage or BCM open internally) in the R DRL relay control circuit.
    • The BCM can only test for this condition with the R DRL relay energized.
    • This condition must be present for 2 seconds.

Action Taken When the DTC Sets

Stores a DTC B0503 in the BCM memory.

Conditions for Clearing the DTC
    • This DTC requires an ignition cycle in order to change from current to history.
    • The BCM no longer detects a high voltage level in the R DRL relay control circuit only with the R DRL relay energized.
    • A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • Use the IPC clearing DTCs feature.
    • The BCM receives the Clear Code command from the scan tool.

Diagnostic Aids
    • The following conditions may cause an intermittent malfunction:
       - There is an intermittent open or short to voltage in the R DRL relay control circuit.
       - There is low resistance in the relay coil.
       - There are poor connections at the BCM, the I/P fuse block, or the R DRL relay terminals.
       - The R DRL relay is shorted to voltage internally.
    • If the BCM is open internally, or if the R DRL relay control circuit is shorted to voltage, the R DRL will remain OFF at all times, butthe RH turn signal will still function normally.
    • If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This canoften cause the malfunction to occur. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

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

    2.

  2. Tests for voltage at the coil side of the R DRL relay. The APPROACH fuse supplies power tothe coil side of the R DRL relay.

    3.

  3. Verifies that the BCM is providing ground to the R DRL relay.

    4.

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

    5.

  5. Tests for a short to voltage in the R DRL control circuit.

Step

Action

Yes

No

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

Connector End View Reference: Master Electrical Component List

1

Did you perform the Lighting System 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 R DRL relay ON and OFF.

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

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the R DRL relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side supply circuit of the R DRL relay with a test lamp that is connected to a good ground. Refer to Power Distribution Schematics in Wiring Systems for electricalcenter circuit identification.

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 R DRL relay and the coil side supply circuit of the R DRL relay. Refer to Power Distribution Schematics in Wiring Systemsfor electrical center circuit identification.
  2. With a scan tool, command the R 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 R DRL relay for a short to battery positive voltage.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 R 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 R 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 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 the open or poor connection in the coil side supply circuit of the R DRL relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

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

Did you complete the replacement?

Go to Step 13

--

12

Important: Perform the BCM reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System.

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 Setting the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK