General System Description

Computer Control Input And Output Chart:

Computer And Emission Control System Diagram:

SYSTEM OVERVIEW
The term used by Nissan to identify the Computerized Engine Control System is ECCS (Electronic Concentrated Engine Control System). The system is comprised of an ECM (electronic control unit/module), sensors (input devices) and actuators (output devices). The ECCS system also has built-in Self-Diagnostics and a Fail-Safe system.

SELF-DIAGNOSTICS
The ECM monitors several circuits and components to determine if they are functioning properly. If a malfunction is detected the "CHECK ENGINE" lamp will be illuminated to alert the driver that a problem is occuring. The lamp will remain illuminated as long the fault is present. The ECM will store a code in its memory to aid the technician in diagnosis. If the lamp turns off, the fault is no longer present, but the code will be stored for 50 attempted engine starts or until the code is cleared from the memory. This aids in diagnosing intermittant problems.

FAIL-SAFE OPERATION
The ECM will substitute an input signal in the event of a failure in the air flow meter, engine temperature sensor or throttle sensor circuits. The engine will operate at reduced capacity to allow the vehicle to be driven until repairs can be made.