Toyota Previa 1991-1997 Repair Information

General Information


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. On earlier systems, the fuel management was performed by the EFI computer; in the current system, the control unit also oversees ignition timing and advance, EGR function, idle speed control (ISC system), Electronically Controlled Transmission (ECT) function as well as on-board diagnostics and back-up or fail-safe functions. 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.