Toyota 2VZ-FE, Manual

Page: 108 / 324

The EFI system is composed of three basic sub–systems: Fuel, Air Induction and Electronic Control Systems.
FUEL SYSTEM
Fuel is supplied under constant pressure to the EFI injectors by an electric fuel pump. The injectors inject
a metered quantity of fuel into the intake manifold in a accordance with signals from the ECU (Electronic Control
Unit).
AIR INDUCTION SYSTEM
The air induction system provides sufficient air for engine operation.
ELECTRONIC CONTROL SYSTEM
The ES250 2VZ–FE engines is equipped with a which centrally controls the EFI, ESA, ISC, Diagnosis systems
etc. by means of an Electronic Control Unit (ECU–formerly EFI computer) employing a microcomputer.
By means of the ECU, the controls the following functions:
1.
Electronic Fuel Injection (EFI)
The ECU receives signals from various sensors indicating changing engine operation conditions such as:
Intake air volume
Intake air temperature
Coolant temperature
Engine rpm
Acceleration/deceleration
Exhaust oxygen content etc.
The signals are utilized by the ECU to determine the injection duration necessary for an optimum air–fuel
ratio.
2. Electronic Spark Advance (ESA)
The ECU is programmed with data for optimum ignition timing under any and all operating conditions.
Using data provided by sensors which monitor various engine functions (rpm, coolant temperature, etc.),
the microcomputer (ECU) triggers the spark at precisely the right instant. (See IG section)
3. Idle Speed Control (ISC)
The ECU is programmed with target idling speed values to respond to different engine conditions (coolant
temperature, air conditioner ON/OFF, etc.). Sensors transmit signals to the ECU which control the flow of
air through the by–pass of the throttle valve and adjust idle speed to the target value. (See page
FI–44 )
4. Diagnosis
The ECU detects any malfunctions abnormalties in the sensor network and lights a ”CHECK” engine warn-
ing light on the instrument panel. At the same time, the trouble is identified and a diagnostic code is re-
corded by the ECU. The diagnostic code can be read by the number of blinks of the ”CHECK” engine warn-
ing light when terminals TE1 and E1 are connected. The diagnostic codes are refer to the later page. (See
page
TR–9 )
5. Fail–Safe Function
In the event of the sensor malfunctioning, a back–up circuit will take over to provide minimal driveability,
and the ”CHECK” engine warning light will illuminate.
– EFI SYSTEM Description
FI–3