GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) is the control center of the fuel injection system. It constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The ECM also performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the malfunction indicator lamp (MIL), and store a DTC or DTCs which identify the problem areas to aid the technician in making repairs. An electrically erasable programmable read only memory (EEPROM) is used to house the program information and the calibrations required for engine, transmission, and powertrain diagnostics operation. The DTC will be stored when the ECM detects a corrupted serial peripheral interface (SPI) communication between the main central processing unit (CPU) and the output driver I/C.

Conditions for Setting the DTC

    • The ignition switch is turned to ON.
    • Battery voltage is greater than 11 volts.

Action Taken When the DTC Sets

    • The MIL will illuminate.
    • The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
    • A history DTC is stored.

Conditions for Clearing the MIL/DTC

    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

Step

Action

Yes

No

1

Perform an On-Board Diagnostic System Check.

Was the check performed?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn the ignition OFF.
  2. Replace the engine control module (ECM). Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 3

--

3

  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the Conditions for Setting the DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?

Go to Step 4

Go to Step 2

4

Are any DTCs displayed that have not been diagnosed?

Go to applicable DTC table

System OK