GM Service Manual Online
For 1990-2009 cars only

Circuit Description

This diagnostic DTC is used to determine when the EBTCM has lost the ability to provide rough road data to the PCM for misfire detection (DTC P0300). When the PCM sees this condition is present via serial data. DTC P1380 will set.

Conditions for Setting the DTC

Test Conditions

    •  Engine speed 7969 RPM or less.
    •  Engine load 79.7% or less.
    •  DTC P0300 is set and requesting the MIL ON.

Failure Condition

Rough road indicator not being sent by EBTCM.

Action Taken When the DTC Sets

    •  The Malfunction Indicator Lamp (MIL) will not illuminate.
    •  No message will be displayed.

Conditions for Clearing the DTC

    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Diagnostic Aids

If this DTC is set along with DTC P0300, it may represent an invalid misfire due to a loss of rough road data.

Several ABS system problems could cause a loss of rough road indication from the EBTCM. All ABS/TCS system problems and DTCs should be corrected first. Then duplicate the conditions under which DTC P1380 set and see if the problem reoccurs.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. If this DTC is set current, refer to ABS diagnosis and diagnose any EBTCM related (ABS/TCS) DTCs before diagnosing any PCM DTCs. If no EBTCM DTCs are present, perform the ABS System Check

  2. If this DTC is history, check for any current or history EBTCM DTCs and diagnose those before diagnosing any PCM DTCs.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2

  1. Using a scan tool select DTC INFO.
  2. Check if this DTC has failed this ignition cycle.

Has the DTC failed?

--

Go to EBTCM system diagnosis

Go to Step 3

3

Check the EBTCM system for any history ABS/TCS DTCs or system problems.

Were any DTCs or problems noted?

--

Go to EBTCM system diagnosis

Fault not present. Refer to Diagnostic Aids