Engine Control Module: Description and Operation

PURPOSE
The ECM provides precise control of fuel injection to ensure optimum performance and strict emissions compliance. It is located under the left front seat.

OPERATION
The ECM performs system control functions such as fuel injection and ignition timing control. In order to maintain optimum air/fuel ratio through its control of the fuel injection system, the ECM monitors exhaust gas oxygen content by way of input from an oxygen sensor. When adjustments are needed, the ECM varies injector pulse width ("ON" time) as the means of controlling air/fuel ratio. Factors such as engine temperature, intake air volume and engine speed are also factored into ECM calculations.

ADAPTIVE SYSTEMS
DME has several adaptive system including lambda control, cylinder filling control, and knock control. DME unit will lose its adaptive memory and any stored fault codes, if battery or control unit connector is disconnected and engine must run for about 10 minutes at normal operating temperature after the next start for control unit to adapt anew.

SELF DIAGNOSIS
When the ECM detects a fault, the "CHECK ENGINE" lamp on the instrument cluster will illuminate. It will remain lit with ignition "ON" until the fault is corrected. A record of the fault is stored in ECM memory as a numbered code.