Engine Control Module: Description and Operation

The Electronic Control Module is a metal cased box (located in passenger compartment) containing electronic circuitry which electrically controls and monitors air/fuel and emission systems on Computer Command Control, and turns on the "CHECK ENGINE" light when a malfunction occurs in the system. The ECM mainly controls the following items:

- Air Injection Reactor (AIR) system
To reduce HC and CO emission, this system draws in air into exhaust ports to accelerate oxidation.

- Exhaust Gas Recirculation (EGR) system
To reduce NOx emission, part of the exhaust gases are recirculated through the EGR valve to the intake manifold to lower the maximum combustion temperature.

- EFE system
The electric EFE device heats the incoming air/fuel mixture to improve vaporization and driveability on cold driveaway. The ECM controls it through the EFE relay.

- Coasting fuel cut system
During deceleration, this system cuts off part of the fuel in the slow circuit of the carburetor.

- Diagnosis
The ECM can detect malfunctions in the system. If a malfunction occurs, the ECM turns on the "CHECK ENGINE" light. A diagnostic code can be obtained from the ECM through the "CHECK ENGINE" light. This code will indicate the area of the malfunction.