General System Description

Fig. 130 Electronic Concentrated Engine Control System:

The term used by Nissan to identify the computerized engine control system is ECCS (electronic concentrated engine control system). This system is comprised of an ECU (electronic control unit) or central processor, several sensors or input devices and actuators or output devices. All components and circuits must work in conjuction with each other for the system to control emissions and maintain fuel economy and performance at optimum levels.
In addition the system has two other features:

1. SELF-DIAGNOSTICS
The ECU monitors several circuit and components to determine if they are functioning properly. If a malfunction is detected in certain circuits the "CHECK ENGINE" lamp (California only) will be illuminated to alert the driver that a problem is occuring. The lamp will remain illuminated as long the fault is present. The ECU 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.

2. FAIL-SAFE OPERATION
The ECU will substitute an input signal in the event of a failure in the air flow meter or 1 fuel injector circuit. The engine will operate at reduced capacity to allow the vehicle to be driven until repairs can be made.