Electronic Control System - Toyota 4A-F Repair Manual

Th.
EFI _v.tem i. compoNd of thr •• b •• lc sub·
.ystem: Induction, Air Induction and
FUI'

Electronic Control System.

FUEL SYSTEM
fU41
i. supplied uode. conttant pressure to the EFI
inj ec tors by In elKlne fuel pump. The injectors
ct metered
i nj e qU8ntity
I
mlnifold in Iccordance with signels from Ihe EeU
(Electronic Control Unit).
.
AIR INDUCTION SYSTEM
The i r induction system p«>vides sufficient ei. for
..,gine operat io n.
ELECTRONIC CONTROL SYSTEM
The 4A·GE engine is eQijipped
Computer Control System creeS) which centrally
m r
controls th, EFI. E$A,
mllln, of en Electronic Control Unit (EeU-fo
co pu t e ) employirog
EFt
meens of the EeU, the TeeS controls the
By
following functions:
1 .
Electronic Fuel Injection IEF!)
The ECU receives signals from various sen­
sors indicating chllnging angine
conditions such as:
Inleke menifold absolute
(w/o Air flow meter)
Intake air volume
(wI Air flow meter)
Intake air temperature
Coolant temperature
Engine rpm
AcceleretionJdeceleration
E .. haust o .. ygen content
These s nals
ig
determine Ihe injection duration
an optimum air-fuel ratio.
2.
Electronic Spark Advance (ESA)
The ECU is programmed with dele for
optimum ignition timing
Openlling conditions. Using deta provided
sensors which monitor various eogine func­
tions (rpm, coolant
microcomputer (ECUI triggers the spark at
precisety the right insUlnt. lSee IG sectionl
EFI SYSTEM
of the Imeke
fuel into
II
wi th
8
Oiagnosi. systems, etc. by
microcomputer.
Opefilting
pressure
TWC) etc.
(wI
utilized the ECU to
are by
necessary
under eny end all
temperature. elc.). the
System Description
3.
Diagl)Qsls
The fCU delects any malfunctions or
maltias in the sensOf network and �ghls
check engine weming light
panel. At the same time. the t.ouble is iden·
t f
i
the ECU. The di&gnostic code clln be read
the number of blinks of
warning light whe .. terminals T
short-circuited. The diagnostic codes
refer
ISee pege FI-25 or
fail-Safe Function
4.
In Ihe event of the sensor ma
b
m
warning light will
Toyote
r m e r l
y
for
by
ed and
i a diegnostic
to the la le r page.
26)
-
eck up circuit will take over to
i nimal driveabititv. and the
�ght.
I
abnor­
by
on the instrument
code is recorded
by
'nI
check engine
the
nd E 1
e
ani
o ng
I
fa c io
l n t i .
providll
check engine