The engine control module (ECM) interacts with many emission related components and systems. The ECM also monitors emission related components, and systems, for deterioration. The on-board diagnostics monitor the system performance and a diagnostic trouble code (DTC) sets if the system performance degrades.
The ECM constantly monitors the information from various sensors and other inputs, and controls the systems that affect the vehicle performance and 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 condition area is identified by the particular DTC that is set. This aids the technician in making repairs.
The engine control module (ECM) can supply 5 volts, 12 volts, or ground to various sensors or switches. Voltage is supplied through pull-up resistors to the regulated power supplies within the ECM. In some cases an ordinary shop voltmeter will not give an accurate reading due to low input resistance. A DMM with at least 10 megaohms input impedance is required in order to ensure accurate voltage readings.
When a malfunction occurs within the engine control system, the engine control module (ECM) maintains control of the system with Default Actions. Default Actions are calculated values, and/or calibrated default values, that are stored within the ECM. A certain level of engine performance is possible when a malfunction occurs dependant on the Default Actions taken. The ECM Default Actions prevent a complete loss of engine performance.
The malfunction indicator lamp (MIL) is located on the instrument panel cluster (IPC), or the driver information center (DIC). The MIL is controlled by the engine control module (ECM) and illuminates when the ECM detects a condition that affects the vehicle emissions.
Removal & Installation
- Disconnect the negative battery cable.
- Disconnect the Engine Control Module (ECM) connectors.
- Remove the ECM retaining nuts.
- Remove the ECM from the ECM mount.
- Position the ECM in place and tighten the retaining bolts to 35 inch lbs. (4 Nm).
- Connect the ECM connectors.
Connect the negative battery cable.
NOTEIf the ECM is replaced, it must be programmed, the Crankshaft Position System Variation Learn procedure and Idle Learn procedure must be performed.