GM Service Manual Online
For 1990-2009 cars only

Circuit Description

This diagnostic test checks for the absence of serial data from the EBTCM. This data is needed for misfire diagnosis (DTC P0300).

Conditions for Setting the DTC

Test Conditions

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

Failure Condition

After 5 seconds from receiving valid data, no serial data is received from the 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.

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

Using a scan tool select DTC INFO ckeck 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