System Description

The computerized engine control system is built around an Electronic Control Unit (ECU). The ECU monitors up to 13 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 (MPFI) controls fuel delivery. Fuel is injected into the intake manifold before the intake valve in precise amounts through electronically 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.

The ECU has the ability to do a self-diagnosis to check for problem areas within its network. It receives input signals from sensors that react to changing driving conditions, and if these signals are out of range or do not exist, fault codes are generated and stored in its memory. Fault codes can be generated from faulty output devices also, and the ECU can check these using the signals that are sent back via the input sensors.


ECU INPUTS ECU OUTPUTS

^ Battery Voltage ^ Electric Fuel Pump Relay
^ Manifold Absolute Pressure ^ B + Latch Relay
^ Coolant Temperature ^ Oxygen Sensor Heater Relay
^ Manifold Air Temperature ^ A/C Compressor Clutch Relay
^ Exhaust Oxygen Sensor ^ Fuel Injectors
^ Engine Speed (crankshaft position) ^ Idle Speed Stepper Motor
^ Throttle Position Sensor ^ EGR Valve Solenoid
^ Injector Sync Signal ^ Ignition Power Module (MPA)
^ A/C Select Signal ^ Shift Indicator Lamp (Manual Transmissions Only)
^ A/C Request Signal
^ Neutral Safety Switch (gear selection-automatic
transmission)
^ Knock Sensor
^ Start Signal