Toyota Supra 1990 Manual page 178

FI-4 EFI SYSTEM - System Description
The EFI system is composed of 3 basic sub sys-
tems; Fuel, Air Induction and Electronic Control
Systems.
FUEL SYSTEM
An electric fuel pump supplies sufficient fuel, un-
der a constant pressure, to the injectors. These in-
jectors inject a measured quantity of fuel into the
intake parts in 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 7M-GE and 7M-GTE engines are equipped with
a Toyota Computer Control System (TCCS) which
centrally controls the EFI, ESA, Diagnosis systems,
etc. by means of an Electronic Control Unit (ECU
formerly EFI computer) employing a
microcomputer.
By means of the ECU, the TCCS controls the fol-
lowing functions:
1. Electronic Fuel Injection (EFI)
The ECU receives signals from various sensors
indicating changing engine operating condi-
tions such as:
Exhaust oxygen content
Intake air volume
Intake air temperature
Coolant temperature
Engine rpm
Acceleration/deceleration etc.
These signals are utilized by the ECU to de-
termine the injection duration necessary for an
optimum air-fuel ratio.
2. Electronic Spark Advance (ESA)
The ECU is programmed with data for opti-
mum ignition timing under any and all operat-
ing conditions. Using data provided by sensors
which monitor various engine functions (rpm,
A/C signal, coolant temperature, etc.), the
microcomputer (ECU) triggers the spark at pre-
cisely the right instant. (See IG section)
3. Idle Speed Control (lSC)
The ECU is programmed with target engine
speed values to respond to different engine
conditions (coolant temperature, air condition-
er 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 pages FI-44, 65, 106)
4. Diagnosis
The ECU detects any malfunctions or abnor-
malties in the sensor network and lights the
"CHECK ENGINE" warning light on the instru-
ment panel. At the same time, the trouble is
identified and a diagnostic code is recorded by
the ECU.
(See page FI-26)
5. Fail-Safe Function
In the event of computer malfunction, a back-
up circuit will take over to provide minimal
drivability. Simultaneously, the "CHECK EN-
GINE" warning light will come on.