GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 2003 🢒 Unit Repair 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 DTC P1381

Circuit Description

This diagnostic will detect a loss of serial communication from the electronic brake control module (EBCM) to the control module. This serial communication is essential in order to distinguish misfire from a rough road condition.

Conditions for Running the DTC
    • The vehicle speed is 2 km/h (1 mph).
    • The engine speed is less than 5800 RPM.
    • The engine load is less than 89 percent.
    • Engine misfire is detected.

Conditions for Setting the DTC

A serial data malfunction is preventing the powertrain control module (PCM) from receiving rough road detection data.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Diagnostic Aids

Check for the following conditions:

An intermittent may be caused by any of the following conditions:

    • A poor connection
    • Rubbed through wire insulation
    • A broken wire inside the insulation

Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step isolates an open serial data circuit from the EBCM system.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Check for any U-Codes.

Did you find any U-Codes?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Disconnect the PCM and EBCM.
  2. Check the serial data circuit between the PCM and the EBCM for an open.

Did you find a problem?

Go to Step 4

Go to A Diagnostic System Check -- ABS in Antilock Brake System

4

Repair the circuit as necessary. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Is the action complete?

Go to Step 5

--

5
  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select the DTC and the specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

Go to Step 6

Go to Step 2

6

Does the scan tool display any additional undiagnosed DTCs?

Go to Diagnostic Trouble Code (DTC) List

System OK