Toyota Celica, Corolla, ECHO & MR2 1999-05

Description & Operation


The Electronic Fuel Injection (EFI) system precisely controls fuel injection to match engine requirements. This in turn reduces emissions and increases drivability. The ECM receives input from various sensors to determine engine operating conditions. These sensors provide the input to the control unit which determines the amount of fuel to be injected as well as other variables such as idle speed. These inputs and their corresponding sensors include:

Manifold Absolute Pressure (MAP) sensor
Intake Air Temperature (IAT) sensor
Engine Coolant Temperature (ECT) sensor
Engine speed (RPM)
Throttle valve opening-Throttle Position Sensor
Exhaust oxygen content-Oxygen Sensor

Fuel injected engines are equipped with the Toyota Computer Control System (TCCS). This integrated control system allows the Engine Control Module (ECM) to control other systems as well as the fuel injection. The control unit is a sophisticated micro-computer, receiving input signals from many sources and locations on the vehicle. It is capable of rapid calculation of many variables and controls several output circuits simultaneously. This system is broken down into 3 major sub-systems: the Fuel System, Air Induction System and the Electronic Control System. Keeping these divisions in mind will shorten troubleshooting and diagnostic time. An electric fuel pump supplies sufficient fuel, under a constant pressure, to the injectors. These injectors allow a metered quantity of fuel into the intake manifold according to signals from the ECM. The air induction system provides sufficient air for the engine operation. This system includes the throttle body, air intake device and idle control system components.