Computers and Control Systems: Description and Operation

The computerized engine control system is built around an Electronic Control Unit (ECU). The ECU monitors up to 12 inputs and responds with appropriate outputs to manage fuel delivery, ignition timing, and emission control devices. As operating conditions change, the ECU adjusts injector pulse width and ignition timing for optimum performance and fuel economy.
The Throttle Body Fuel Injection System (TBI) controls fuel delivery. This system is a single point, pulse time system that injects fuel through an electrically operated fuel injector into the throttle body above the throttle plate. The fuel injection pulse width, the period of time that the injector is energized causing fuel to be released into the throttle body, is controlled by the ECU.



ECU INPUTS

- Start Signal
- Engine Coolant Temperature
- Intake Manifold Air Temperature
- Intake Manifold Absolute Pressure
- Throttle Position
- Exhaust Gas Oxygen Content
- Battery Voltage
- A/C Select & Request
- Engine Knock
- Closed Throttle Switch
- Neutral Safety Switch


ECU OUTPUTS

- Electric Fuel Pump Relay
- B + Latch Relay
- A/C Compressor Clutch Relay
- Idle Speed Control (ISC) Motor
- Ignition Control Module (ICM)
- EGR Solenoid
- Shift Indicator Lamp (Manual Transmissions Only)
- Engine Speed (crankshaft position)
- Fuel Injector