GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century 🢒 DTC 🢒 DTC P1381 Misfire Detected - No Communication with Brake Control Module

Circuit Description

The PCM uses the rough road information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. The EBCM/EBTCM transmits rough road information based on inputs from the wheel speed sensors. If a loss of communication occurs which causes the PCM not to receive rough road information while DTC P0300 Engine Misfire Detected is requesting the MIL, DTC P1381 will set.

Conditions for Running the DTC
    •  Engine load is less than 87%.
    •  Engine speed is less than 5000 RPM.
    •  Vehicle speed is greater than 10 mph.
    •  A misfire DTC is occurring and requesting the MIL to be illuminated.

Conditions for Setting the DTC

The PCM is detecting a loss of communication with the EBCM / EBTCM for at least 5 seconds.

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Diagnostic Aids

Check for the following conditions:

Important: :  Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

    •  Poor terminal connection.
         Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems.
    •  Damaged harness.
         Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems.
    •  Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

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

  1. Ensures that the EBCM/EBTCM is capable of transmitting serial data on the Class II serial data circuit.

    2.

  2. Checks the Class II serial data circuit at the EBCM/EBTCM for correct voltage.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain on-Board Diagnostic (OBD) System Test performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Turn on the ignition switch.
  2. Select chassis application on the scan tool.
  3. Attempt to display ABS data on the scan tool.

Can ABS data be displayed?

--

Go to Step 3

Go to Step 4

3
  1. Test the serial data circuit for an open or a poor connection between the PCM and the EBCM.
  2. If a problem is found, repair as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs .

Was a problem found?

--

System OK

Go to Diagnostic Aids

4

  1. Turn off the ignition switch.
  2. Disconnect the EBCM.
  3. Turn on the ignition switch.
  4. Using a J 39200 DMM measure voltage on the serial data circuit at the EBCM harness connector.

Does voltage vary within a range between the specified values?

1.0-5.0V

Go to Step 5

Go to Step 6

5
  1. Test for a poor connection at the EBCM.
  2. If a problem is found, replace faulty terminal(s) as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs .

Was a problem found?

--

Go to Step 7

Go to Step 6

6
  1. Test for an open in the serial data circuit to the EBCM. Refer to Diagnostic System Check - Data Link Communications .
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 7

Go to Diagnostic System Check - ABS

7
  1. Turn on the ignition switch.
  2. Select chassis application on the scan tool.
  3. Attempt to display ABS data on the scan tool.

Can ABS data be displayed?

--

System OK

Go to Step 4