Toyota Land Cruiser 1988 Repair Manual page 134

EFI SYSTEM - System Description
The EFI system is composed of three basic
subsystems: Fuel Induction, Air Induction
and Electronic Control Systems.
FUEL SYSTEM
Fuel is supplied under constant pressure to the
EFI injectors by an electric fuel pump. The injec-
tors inject a metered quantity of fuel into the in-
take manifold 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 3F-'E engine is equipped with a Toyota Com-
puter Control System (TCCS) which centrally
controls the EFI, ESA, ISC, Diagnosis systems,
etc. by means of an Electronic Control Unit (ECU
-formerly EFI computer) employing a microcom-
puter.
By means of the ECU, the TCCS controls the
following functions:
1. Electronic Fuel Injection (EFI)
The ECU receives signals from various sen-
sors indicating changing engine operating
conditions such as:
Intake air volume
Intake air temperature
Coolant temperature
Engine rpm
Acceleration I deceleration
Exhaust oxygen content etc.
These signals are utilized by the ECU to de-
termine the injection duration necessary for
an optimum air-fuel ration.
2. Electronic Spark Advance (ESA)
The ECU is programmed with data for opti-
mum ignition timing under any and all oper-
ating conditions. Using data provided by
sensors which monitor various engine func-
tions (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 condi-
tioner on/off, etc.). Sensors transmit signals
to the ECU which control the flow of air
through the bypass of the throttle valve and
adjust idle speed to the target value.
(See pages Fl-40, 71)
4. Exhaust Gas Recirculation (EGR)
The ECU controls the EG R system according
a coolant temperature, engine rpm, throttle
angle, vehicle speed and inlet air flow rate.
5. Air Injection (AI)
The ECU controls the AI system according to
coolant temperature, engine rpm, throttle
angle, vehicle speed and inlet air rate.
6. Diagnosis
The ECU detects any malfunctions or abnor-
malities in the sensor network and lights a
"CHECK" engine warning light on the in-
strument panel. At the same time, the trouble
is identified and a diagnostic code is
recorded by the ECU. The diagnostic code
can be read by the number of blinks of the
''CHECK" engine warning light when termi-
nals TE1 and E1 are short-circuited. The di-
agnostic codes are refer to the later page.
(See pages Fl-24, 25)
7. Fail-Safe Function
When an abnormality occurs in any of the
ECU input signals, the ECU substitutes a
standard valve stored in the microcomputer
memory in order to prevent engine malfunc-
tion. Also, if the abnormality is serious, the
ECU stops the engine.
8. Back-Up Function
Even when an abnormality occurs in the
ECU provides regular fuel injection and con-
trol of the ignition timing to provide vehicle
driveability.