Computers and Control Systems: Description and Operation

Fig. 1 I-TEC control system.:

This system, Fig. 1, is an electronically controlled emission control system that monitors and controls the various engine operating conditions through sensors and actuators. A micro computer control unit processes the signals from the sensors, then controls the ignition timing/dwell, fuel injection volume/air fuel ratio and the vacuum switching valve.
The I-TEC system has a built in diagnostic system that recognizes and identifies problems in the electrical circuitry and not in the sensors, actuators or engine. A ``Check Engine'' lamp in the instrument panel notifies the operator of the vehicle that a problem exists. This same light is used with the built in diagnostic system to aid the service technician in locating and repairing problems by flashing a series of trouble codes which identify the problem area.
This system also has a ``Back-Up Control'' mode which allows near normal operation of the vehicle until the necessary repairs are performed should a malfunction occur.