Engine Control Module: Description and Operation

The ECM controls the following functions:

1. Multiport Fuel Injection (MFI)

The ECM receives signals from various sensors indicating changing engine operating conditions such as:

Intake manifold absolute pressure

Intake air temperature

Engine coolant temperature

Engine rpm

Throttle valve opening angle

Exhaust oxygen content, etc.

These signals are utilized by the Electronic Control Module (ECM) to determine the injection duration necessary for an optimum air-fuel ratio.

2. Electronic Spark Advance (ESA)

The ECM is programmed with data for optimum ignition timing under all operating conditions. Using data provided by sensors which monitor various engine functions (rpm, engine coolant temperature, etc.) the microcomputer (ECM) triggers the spark at precisely the right instant.

3. Idle-Up Control

The ECM determines the appropriate idle speed according to engine condition and provides the electric signal to the Vacuum Switching Valve (VSV) which controls the bypass air.

4. Exhaust Gas Recirculation (EGR)

The ECM controls the EGR system according to coolant temperature, engine rpm and intake manifold absolute pressure. The electric signal from the ECM is transmitted to the VSV which controls the EGR valve.

5. Diagnosis

The ECM detects any malfunctions or abnormalities in the sensor network and lights a malfunction indicator lamp on the instrument panel. At the same time, the trouble is identified and a diagnostic code is recorded by the ECM. The diagnostic trouble code can be read by the number of blinks of the malfunction indicator lamp when terminals TE1 and E1 are connected. For the diagnostic trouble codes.

6. Fail-Safe Function

In the event of a sensor malfunction, a back-up circuit will take over to provide minimal driveability, and the malfunction indicator lamp will light up.