Preliminary Information

Engine Control Module (ECM) Description:

This vehicle is equipped with advanced diagnostic capabilities. The OBD II system is a much more complex system than the prior on-board diagnostics. The Engine Control Module (ECM) interacts with many more emission related components and Systems, and monitors emission related components and systems for deterioration. Most of these diagnostics will detect a problem before the customer notices a change in the driveability. OBD II diagnostics monitor the system performance and a Diagnostic Trouble Code (DTC) will set if the system performance degrades.

The Malfunction Indicator Lamp (MIL) operation and the DTC storage are dictated by the DTC type. A DTC is ranked as a Type A or Type B if the DTC is emissions related. Type C is not emissions related. Each DTC type has its own set of MIL operation, DTC storage, and a DTC clearing criteria.

The ECM is in the engine compartment, inside the relay center. The ECM is the control center of the engine controls system. The ECM controls the following components:
^ The fuel injection system
^ The ignition system
^ The emission control systems
^ The on-board diagnostics for engine functions
^ The A/C and multi-ram systems
^ The Throttle Actuation Control (TAC) system

The ECM constantly looks at the information from various sensors and other inputs, and controls the systems that affect the vehicle performance and the emissions. The ECM also performs diagnostic tests on various parts of the system. The ECM can recognize operational problems and alert the driver via the MIL. When the ECM detects a malfunction, the ECM stores a DTC. The problem area is identified by the particular DTC that is set. This aids the technician in making repairs.

The ECM connects to the engine wiring harness by two 64-pin connectors.