Toyota Tercel 1984-1994 Repair Guide

System Description


The Electronic Fuel Injection (EFI) system precisely controls fuel injection to match engine requirements, reducing emissions and increasing driveability. The electric fuel pump supplies fuel to the pressure regulator. The fuel injectors are electric solenoid valves which open and close by signals from the Electronic Control Module (ECM). The ECM is also known as the Electronic Control Unit (ECU).

The ECM receives input from various sensors to determine engine operating conditions. This allows the ECM to determine the correct amount of fuel to be injected by it's preset program. These inputs and their corresponding sensors are:

Intake manifold absolute pressure - Manifold Absolute Pressure (MAP) or vacuum sensor
Intake air temperature - Intake Air Temperature (IAT) sensor
Coolant temperature - Water temperature sensor
Engine speed - reference pulse from the distributor
Throttle valve opening angle - Throttle Position Sensor (TPS)
Exhaust oxygen content - Oxygen sensor