Powertrain Management: Description and Operation

Computer And Emission Control Circuit Diagram:

ECM Input/Output Chart:

PURPOSE
The Electronic Concentrated Engine Control System (ECCS) is used to provide precise control of the air-fuel ratio to the stoichiometric point. The Three way catalyst can then better reduce CO, HC and NOX emissions. In "closed loop," the Electronic Control Module (ECM) adjusts the injector pulse width according to the sensor input voltages. This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).

"Open loop" refers to when the ECM detects any of the following conditions. Feedback control stops in order to maintain stabilized fuel combustion.
1. Deceleration and acceleration
2. High load, high speed operation
3. Engine idling
4. Malfunction of oxygen sensor or its circuit
5. Insufficient activation of oxygen sensor at low engine coolant temperature
6. Engine starting
7. High engine coolant temperatures
8. After shifting from "N" to "D"

OPERATION
The Electronic Concentrated Engine Control System (ECCS) consists of sensors which detect the engine condition, the Engine Control Module (ECM) which controls the engine on the basis of the sensor signals, and actuators which operate under control of the ECM. The ECM controls the fuel injection, idle speed, ignition timing, engine cooling fan, Exhaust Gas Recirculation (EGR), evaporative canister system, and the fuel pump. In addition, the ECM is provided with 2 diagnostic test modes (DTM) to facilitate troubleshooting in case of failure.

In the event of a component or circuit failure of certain sensors or actuators, the ECM is programed with a Fail-Safe feature. This will allow the vehicle to be driven in a limited capacity.