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 15 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 Multi-Point Fuel Injection System (MPI) controls fuel delivery. Fuel is injected into the intake manifold before the intake valve in precise amounts through electrically operated injectors. The injectors are fired in a specific sequence by the ECU. The ECU constantly adjusts the amount of fuel injected to meet changing operating conditions by controlling injector pulse width (the length of time the injector is energized).
The ECU also adjusts the ignition timing by controlling the ignition coil operation through the ignition control module.



ECU INPUTS

- Battery Voltage
- Ignition
- Speed Sensor
- A/C Select Signal
- A/C Request Signal
- Starter Relay - (engine crank signal)
- Manifold Absolute Pressure (MAP) Sensor
- Throttle Position
- Manifold Air Temperature (MAT) Sensor
- Engine Coolant Temperature
- Sync Signal
- Ignition Relay - ON Signal
- Engine Knock Sensor
- Neutral Safety Switch (gear selection-auto trans.)
- Exhaust Oxygen (O2) Sensor





ECU OUTPUTS

- Idle Speed Regulator
- Fuel Injectors
- Electric Fuel Pump Relay
- Oxygen Sensor Relay
- Shift Lamp
- B + Latch Relay
- EGR Valve Solenoid
- A/C Relay