GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Rough roads cause torque on the tires that is transmitted to the powertrain. This slows down the crankshaft giving the appearance of a misfire. The electronic brake and traction control module (EBTCM) determines rough road surfaces using input from the wheel speed sensors. The EBTCM then sends the rough road data to the powertrain control module (PCM) via class 2 serial data. The powertrain control module (PCM) uses the rough road data to enhance the misfire diagnostic. The data allows the PCM to distinguish the crankshaft speed variations caused by rough road surfaces from those caused by true misfires. If the EBTCM is unable to identify rough road conditions while the PCM detects a misfire condition, DTC P1380 will set.

Conditions for Running the DTC

    • The engine load is less than 100 percent.
    • The engine speed is less than 6,500 RPM.
    • The vehicle speed is more than 1 km/h (0.6 mph).
    • A misfire diagnostic trouble code (DTC) is occurring and requesting the malfunction indicator lamp (MIL) to be illuminated.

Conditions for Setting the DTC

The PCM detects an EBTCM rough road sensing error.

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

DTC P1380 set indicates that the antilock brake system/traction control system (ABS/TCS) system has detected a malfunction which will not allow the EBTCM to transmit correct rough road data to the PCM.

If the condition is intermittent, refer to Intermittent Conditions .

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Diagnostic System Check - ABS

Go to Diagnostic System Check - Engine Controls