GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 SRX 🢒 Accessories 🢒 Navigation Systems 🢒 DTC B3903

Circuit Description

The electronic brake control module (EBCM) supplies voltage to the brake pedal position sensor relay coil side voltage supply circuit when the stop lamps are active. The coil side control circuit of the brake pedal position sensor relay is permanently grounded at G402.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3903 Stoplamp Relay Circuit

Conditions for Running the DTC
    • The EBCM control module must be powered.
    • This test is run continuously.

Conditions for Setting the DTC

If the brake pedal position sensor relay coil side voltage supply circuit is out of range for more than 30 milliseconds.

Action Taken When the DTC Sets

When DTC B3903 is set the following will occur:

The service vehicle soon lamp will illuminate.

Conditions for Clearing the DTC
    • The current DTC will clear when the fault is no longer present.
    • The ignition key must be cycled OFF and ON.
    • A history DTC clears after 100 consecutive ignition cycles in which no faults have occurred.
    • Clear the DTC with a scan tool.

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

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. Retrieve DTCs.

Is the DTC retrieved as a current DTC?

Go to Step 3

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

3

Test the relay coil side voltage supply circuit of the brake pedal position sensor relay for a short to voltage, short to ground, or an open. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Inspect for poor connections at the harness connector of the electronic brake control module (EBCM). 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 6

Go to Step 5

5

Important: Always perform the setup procedure for the EBCM.

  1. Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
  2. Perform the setup procedure for the EBCM.

Did you complete the replacement?

Go to Step 6

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6
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK