Computers and Control Systems: Description and Operation

Computerized Engine Controls:

The engine systems in this vehicle are controlled by a Single Board Engine Controller (SBEC). This controller provides precise air/fuel mixture control for all driving conditions, and regulates ignition timing, emission control devices, cooling fan, charging system, and idle speed. The SBEC is a digital pre-programmed computer that has the ability to update and revise its programming to meet changing operating conditions.

Various sensors provide necessary input for the SBEC to function correctly. These include the Manifold Absolute Pressure Sensor, Throttle Position Sensor, Oxygen Sensor, Coolant Temperature Sensor, and Vehicle Distance Sensors. In addition to these sensors, various switches and relays are used to carry out commands or outputs from the SBEC.

The SBEC tests many of its own input and output circuits. If a fault is found in any major system, this information is either stored in memory or displayed as a light on the instrument panel. If a fault exists, the fault information can be displayed to a technician through the instrument panel CHECK ENGINE lamp or a suitable diagnostic scan tool.

The SBEC contains a voltage regulator and converter that supplies a regulated 8 volts to the distributor's pick-up. The computer also supplies a 5 volt reference to the Throttle Position Sensor (TPS), Manifold Absolute Pressure (MAP) Sensor, and logic circuits.


SBEC INPUTS

- Coolant Temperature Sensor
- Heated Oxygen Sensor
- Manifold Absolute Pressure (MAP) Sensor
- Switch Signals
- Throttle Body Temperature Sensor
- Throttle Position Sensor (TPS)
- Vehicle Distance (Speed) Sensor


SBEC OUTPUTS

- Air Conditioning Clutch Relay
- Automatic Idle Speed (AIS) Motor
- Auto Shutdown (ASD) Relay
- Canister Purge Solenoid
- Check Engine Lamp
- Fuel Injector