Toyota TOYOTA COMPUTER-CONTROLLED SYSTEM Installation guide

training manual
VOLUME 1 STEP 3 /
TCCS
(TOYOTA COMPUTER-
CONTROLLED SYSTEM)

FOREWOR D
This Training Manual has been prepared
for the use of technicians employed by Toyota's overseas
distributors and dealers
. This manual, "TCCS (Toyota Computer-Controlled System)", is Volume 1 of
the thirteen Training Manuals which constitute Step 3 of the program of skills which all Toyota New
TEAM*
technicians should master . It should also be used by the instructor in conjunction
with the
accompanying Instruction Guide .
The titles
of the New TEAM Step 3 Training Manuals are as follows
:
VOL .
TRAINING MANUALS VOL . TRAINING MANUAL S
1 TCCS (Toyota Computer-Controlled System) 8
NVH (Noise, Vibration & Harshness
)
2 Turbocharger & Supercharger 9
Fundamentals of Electronic s
3 Diesel Injection Pump 10 CCS
(Cruise Control System
)
4 ECT ( Electronically-Controlled Transmission)
1 1 Car Audio Syste m
5 Full-Time 4WD
12 Automatic Air Conditioning Syste m
6 TEMS & Air Suspension
13 SRS Airbag & Seat Belt Pretensione r
7
ABS & Traction Control Syste m
It is not enough just to "know" or "understand" - you need to master each task so that you can do
it
. For this reason, theory and practice have been combined in this Training Manual
. The top of each
page is marked either with a Q symbol to indicate that it is a Theory page or a® symbol to indicate
that it is a Practice page
.
Note that in regards to inspection and other procedures mentioned in the Practice section, this
Training Manual contains only the main points to be learned
; please refer to the relevant Repair
Manual(s) for details .
The following notations often occur in this manual, with the meanings as explained :
A potentially hazardous situation which could result in injury to people may occur i
f
CAUTION
instructions are not followed .
NOTICE
Damage to the vehicle or components may occur if instructions are not followed .
NOTE Notes or comments not included under the above two headings .
Information not required to pass the TEAM certification, but which may be useful t o
REFERENCE
instructors and to trainess who wish to gain a deeper knowledge of the subject .
*TEAM : TEAM stands for 'Technical Education for Automotive Maste
ry' , which is a training program divided into three steps
according to the technician's technical level
. This program makes it possible for technicians to receive the appropriate training for their
level in a systematic manner so as to help them achieve the skills and efficiency of skilled technicians in the sho
rt est possible time .

This Training Manual explains the TCCS
engine control system based on the 4A-FE engine . However,
representative engines other than the 4A-FE
engine have sometimes been selected to explain
mechanisms not found" on the 4A-FE engine
. In this way, explanations of as many mechanisms as
possible have been included .
All information contained in this manual is the most up-to-date at the time of publication
. However,
we reserve the right to make changes without prior notice .
TOYOTA MOTOR CORPORATIO
N
©1997 TOYOTA
MOTOR CORPORATION
All rights reserved . This book may not be repro-
duced or copied, in whole or in part, without the
written permission of Toyota Motor Corporation .

TABLE OF CONTENT
S
Page
ABBREVIATIONS AND ECU TERMINAL SYMBOL
S
ABBREVIATIONS . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . 1
ECU TERMINAL SYMBOLS
. . . . . . . . . . . . . . . . . . . . . . 2
OUTLINE OF TCC S
WHAT IS TCCS? .. .. . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
HISTORY OF TCCS ENGINE CONTROL
SYSTEM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1
. Functions of engine control system . . . 8
2 . Construction of engine contro l
system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3
. Engine control system diagram
. . . . . . . . . 1 2
ELECTRONIC CONTROL SYSTE M
GENERAL . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . 13
POWER CIRCUITRY . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . 15
1 . Engine without stepper motor typ e
ISC valve . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 15
2 . Engine with stepper motor typ
e
ISC valve . .. . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
VC CIRCUITRY . . . . . . . . .. . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 16
GROUND CIRCUITRY
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
MANIFOLD PRESSURE SENSO R
(VACUUM
SENSOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
AIR FLOW METER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1 . Vane type .. .. . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2
. Optical Karman vortex type . . . . . . . . . . . . . . 21
3
. Hot-wire type . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 21-
1
THROTTLE POSITION SENSOR . . . . . . . . . . . . . . . . 22
1 . On-off type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2
. Linear type . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . 2 3
G AND NE SIGNAL GENERATORS . . . . . . . . . . .
. 24
1 . In-distributor type . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2 . Cam position sensor type . . . . . . . . ..
. . . . . . 27
3 . Separate type
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 2
8
WATER TEMPERATURE SENSOR . . . . . . . . . . . . . 30
INTAKE AIR TEMPERATURE SENSOR . . . .
. . . 30
OXYGEN SENSOR (02 SENSOR)
. . . . . . . . . . . 30- 1
1 . Zirconia element type
. . . . . . . . . . . . . . . . . . . 30-1
2 . Titania element type
. . . . . . . . . . . . . . . . . . . . . . . . .32
LEAN MIXTURE SENSOR
. . . . . . . . . . . . . . . . . . . . . . . . 33
Page
VEHICLE SPEED
SENSOR . . . . . . . . . . . . . . . .
. . . . . . . . 3 4
1 . Reed switch type . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 34
2 . Photocoupler type . . . . . . . . .
. . . . . . . . . . . . . . . . . 34
3
. Electromagnetic pickup type
. . . . . . . . . . . . 35
4 . MRE type . . . . . . . . . . . . . . . . . .. .. .
. . . . . . . . . . . . . . . . 3 6
STA SIGNAL . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . 38
NSW SIGNAL . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . 38
A/C SIGNAL .... . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . 39
ELECTRICAL LOAD SIGNAL
. . .. . . . . . . . . . . . . . . . . 39
FUEL CONTROL SWITCH O
R
CONNECTOR . . . . . . . .. . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 40
EGR GAS TEMPERATURE SENSOR
. . . . . . . . . . 40
VARIABLE RESISTOR
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
KICK-DOWN SWITCH
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 42
WATER TEMPERATURE SWITCH
. . . . . . . . . . . .
. 42
CLUTCH SWITCH
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
KNOCK SENSOR
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 43
HAC SENSOR
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . 44
VAPOR PRESSURE SENSOR . . . . . . . . . . . . . . . . . .
. . 44
TURBOCHARGING PRESSURE SENSOR
. . . . 44
STOP LAMP SWITCH . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 45
OIL PRESSURE SWITCH . . . . . . . . . . .
. . . . . . . . . . . . . . 45
COMMUNICATIONS SIGNALS
. . . . . . . . . . . . . . . . . 4 5
1 . Throttle opening angle signals
. . . . . . . . . . 45
2 . Throttle opening angle signals fo
r
TRC system . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 45
3 . Cruise control syste
m
communications signal
. . . . . . . . . . . . . . . . . . . . 46
4. TRC system
communications signal . . 46
5 . ABS communications signal
. . . . . . . . . . . . . 46
6 . Intercooler system warning signal
. . . . . 46
7 . EHPS system
communication s
signal . . . . . . . . . . . . . . . . . .. . . . . . . . .
. . . . . . . . . . . . . . . . . 47
8 . Engine speed signal
. . . . . . . . . . . . . . . . . . . . . . . . 47
9 . Engine immobiliser syste
m
communications
signal . . . . . . . . . . . . . . . . . . . . 47
DIAGNOSTIC TERMINAL(S) . . . . . . . . . . . . . .• .••••• 4
8
EFI (ELECTRONIC FUEL INJECTION
)
GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . 49
TYPES OF EFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . 52
1 . D-type EFI . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 52

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Page
DIAGNOSTIC CODES
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8
FAIL-SAFE FUNCTIO
N
FAIL-SAFE FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5
BACK-UP FUNCTIO N
BACK-UP FUNCTION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7
TROUBLESHOOTIN G
GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 149
HOW TO CARRY OU T
TROUBLESHOOTING
. . . . . . . . . . . . . . . . . . . . . . . . . . 150
PRE-DIAGNOSTIC QUESTIONING
. . . . . . . . . . . . . 152
SYMPTOM CHART . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 1 5 4
® CHECKING AND CLEARING DIAGNOSTIC
CODE S
"CHECK ENGINE" LAMP CHECK . . . . . . . . .. .
.
. 159
OUTPUT OF DIAGNOSTIC CODE S
1 . Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . 15 9
2 . Test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 161
CLEARING DIAGNOSTIC CODE . . . . . . . . . .
. . . . .
. 16
2
IS SYMPTOM SIMULATION
. . . . . . . . . . . . . . . . . . . . . . . . . . . 163
® BASIC INSPECTION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
INSPECTION AND ADJUSTMEN T
GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 171
IDLE SPEED AND IDLE MIXTURE . . . . . . . . . . ..
. 172
MANIFOLD PRESSURE SENSO
R
(VACUUM SENSOR) . . . . . . . . . . . . . . . . . . . . . . . . . .
. 175
THROTTLE POSITION SENSO
R
(LINEAR TYPE) AND THROTTL
E
BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . 177
DISTRIBUTOR (G AND NE SIGNALS)
. . . . . . . . 180
INTAKE AIR TEMPERATURE
SENSOR . . . . . . . 181
FEEDBACK CORRECTION . . . . . . . . . . . . . . . . . . .
. . . . 182
Models with oxygen senso r
(02 sensor)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Models with
lean mixture sensor . . . . . . . . . . . 183
VARIABLE RESISTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
ISC VALV E
(DUTY-CONTROL ACV TYPE) . . . . . . . . . . . . . . 186
Pag e
APPENDIX
ENGINE CONTROL SYSTE M
SPECFICATION CHART .. ... . . ..
.. ... . . . ... ... . 18 8
DELETED FOR NEW EDITIO N
. . . . . ... ... . . . ... .. . 118, 119, 125, 126, 141 to 144,
166 and 174

ABBREVIATIONS AND ECU TERMINAL SYMBOLS - Abbreviations
4
ABBREVIATIONS AND ECU TERMINAL SYMBOL S
ABBREVIATION S
ABS Anti-Lock Brake System
ABV Air Bypass Valv e
AC Alternating Current
A/C Air Conditione r
ACIS Acoustic Control Induction System
ACV Air Control Valv e
Al Air Injection
AS Air Suctio n
ASV Air Switching Valv e
A/T Automatic Transmission
BTDC Before Top Dead Center
CA Crankshaft Angl e
CALIF Californi a
CCS Cruise Control System
CO Carbon Monoxid e
DIS Direct Ignition System
DLI Distributorless Ignition
EC European Countrie s
ECT Electronically-Controlled Transmission
ECU Electronic Control Uni t
EFI Electronic Fuel Injection
EGR Exhaust Gas Recirculatio n
EHPS Electro-Hydraulic Power Steering
ESA Electronic Spark Advanc e
FED . Federal
GEN . General Countrie s
HAC High-Altitude Compensation
HC Hydrocarbo n
HIC Hybrid Integrated Circui t
IIA Integrated Ignition Assembly
ISC Idle Speed Contro l
LED Light Emitting Diode
LS Lean Mixture Senso r
MRE Magnetic
Resistance Element
M/T Manual
Transmissio n
NOx Oxides of Nitrogen
OC Oxidation Catalyst
OD Overdrive
02 Oxygen
PS Power Steering
SCV Swirl Control Valve
SST Special Service Tool
SW Switc h
TCCS Toyota Computer-Controlled System
TDC Top Dead Cente r
TDCL *1 Toyota Diagnostic Communication
Link or Total Diagnostic
Communication Lin k
TEMS Toyota Electronically-Modulated
Suspension
Tr Transisto r
TRC*2 Traction Contro l
T-VIS Toyota-Variable Induction System
TWC Three-Way Catalys t
U .S
. United State s
VSV Vacuum Switching Valve
w/ Wit h
w/o Withou t
4WD 4-Wheel-Driv e
In vehicles sold at Lexus dealers in the U .S . and
Canada, this is called the "Total Diagnostic
Communication Link" . In Toyotas sold in other
countries, and in Toyotas sold at Toyota dealers
in the U .S . and Canada, it is called the "Toyota
Diagnostic Communication Link" . In this
manual, it is called the "Toyota Diagnostic
Communication Link"
.
*2 In
the U .S . and Canada, this is abbreviated to
TRAC .
/-- iw 1
c
Abbreviations in accordance with SAE terms
are used for vehicles sold in the U
.S .A . and
Canada . Refer to the Repair Manual for dif-
ferences between SAE terms and Toyota
terms .
Example :
ECM Engine Control Module
(= Engine ECU
)
ECT Engine Coolant Temperature
(= THW)
1

ABBREVIATIONS AND ECU TERMINAL SYMBOLS - ECU Terminal Symbol s
ECU TERMINAL SYMBOL S
SYMBOL MEANING
ABS Anti-Lock Brake Syste m
ACC1 Acceleration Signal No . 1(from
Thro tt le Position Sensor)
ACC2 Acceleration Signal No . 2 (fro m
Throttle Position Sensor)
A/C Air Conditione r
ACMG Air Conditioner Magnetic Clutch
ACT Air Conditioner Cut-Of f
Al Air Injection
AS Air Suctio n
A/D Auto Drive (Cruise Control System)
+B Ba tt e r y
+B1 Ba tt e ry No . 1
BATT Ba tt e r y
BF Ba tt e ry Fail Safe
BRK Brake
DFG Defogge r
E01 Ea
rt
h No
. 01 (Ground)
E02 Ea rt h No . 02 (Ground)
E1 Ea
rt
h No . 1 (Ground)
E2 Ea
rt
h No
. 2 (Ground )
ECT Electronically-Controlled Transmission
ELS Electrical Load Signa l
EGR Exhaust Gas Recirculation
FC Fuel Pump Contro l
FP Fuel Pump Control Relay
FPU Fuel Pressure-U p
FS Fail-Safe Rela y
G Group (Crankshaft Angle Signal )
G1 Group No .
1 (Crankshaft
Angle Signal)
G2 Group No .
2 (Crankshaft
Angle Signal)
G- Group Minus (-
)
HAC High-Altitude Compensatio n
HT Heater (for Oxygen Sensor or Lean
Mixture Sensor )
IDL Idle Switch (in Throttle Position
Sensor )
IGDA Ignition Distribution Signal A
IGDB Ignition Distribution Signal B
IGF Ignition Failure (Confirmation) Signal
IGSW Ignition Switc h
IGT Ignition Timing Signal
SYMBOL MEANIN G
ISC1 Idle Speed Control Signal No . 1
ISC2 Idle Speed Control Signal No
. 2
ISC3 Idle Speed Control Signal No . 3
ISC4 Idle Speed Control Signal No . 4
KD Kick-Dow n
KNK Knock Sensor
KS Karman Signa l
L7 Throttle Valve Opening Signal No
. 1
L2 Throttle Valve Opening Signal No
. 2
L3 Throttle Valve Opening Signal No . 3
LP Lam p
LS Lean Mixture Sensor
LSW Lean Burn Switch
M-REL EFI Main Rela y
N/C Neutral Clutch Switc h
NE Number of Engine Revolutions
Signa l
NE- Number of Engine Revolutions
Signal Minus (- )
NEO Number of Engine Revolutions
Signal Outpu t
No .10 (for Injectors)
No .20 (for Injectors )
NSW Neutral Sta rt Switch
OX Oxygen Senso r
OX + Oxygen Sensor ~+
OIL Oil Pressur e
OD Overdrive
PS Power Steerin g
PSW Power Switch (in Throttle Position
Sensor )
PIM Pressure, Intake Manifol d
R-P Regular or Premium Gasoline Signal
RSC Rota ry Solenoid Valve Close d
RSO Rota
ry
Solenoid Valve Open
SCV Swirl Control Valv
e
SPD Vehicle Spee d
SP2 Vehicle Speed No . 2
SP2- Vehicle Speed No . 2 Minus (-)
STA Sta rt e r
STJ Cold Sta rt Injecto r
2

ABBREVIATIONS AND ECU TERMINAL SYMBOLS
- ECU Terminal Symbol
s
SYMBOL MEANING
STP Stop Lamp Switch
T Test Termina l
TE1 Test Terminal, Engine No . 1
TE2 Test Terminal, Engine No . 2
THA Thermo, Intake Ai r
THG Thermo, Exhaust Gas
THW Thermo, Wate r
TR Traction Contro l
T-VIS Toyota-Variable Induction System
TSW Water Temperature Switc
h
VAF Voltage, Air-Fuel Ratio Control
VB Voltage, Batter y
VC Voltage, Constant
VF Voltage, Feedbac k
VG Voltage, Gram Intake Air
V-ISC VSV Type Idle Speed Control
VS Voltage, Slide Signa
l
VSH Voltage, Sub-Throttle Angle
VTA Voltage, Throttle Angle
VTH Voltage, Throttle Angl e
W "CHECK ENGINE" Warning Lamp
WIN Warning Lamp, Intercooler
F4$
3

b
OW3W

OUTLINE OF TCCS - What is TCCS ?
OUTLINE OF TCC S
WHAT IS TCCS ?
"TCCS" (Toyota Computer-Controlled System) is
the general name for a system which exercises
comprehensive and highly precise control of the
engine, drive train, brake system, and other
systems by means of an ECU* (electronic control
unit), at the heart of which is a microcomputer
.
Previously, TCCS was used as an engine control
system for only EFI (electronic fuel injection),
ESA (electronic spark advance), ISC (idle speed
control), diagnosis, etc
.
Later, control systems utilizing other separate
ECUs were developed and adopted for the
control of systems other than the engine also .
Currently, the term "TCCS" has come to mean a
comprehensive control system which incorpo-
®
rates control systems controlled by various ECUs
to ensure basic vehicle performance, not only
running, turning and stopping .
*At Toyota, a computer which controls each
type of system is called an "ECU"
.
REFERENCE
On some vehicle models, the ECT has its own
ECU, called the "ECT ECU" . (The ECU for
engine control is called the "Engine ECU" in
this case .) On models in which the ECT does
not have its own separate ECU, the ECT uses
the ECU for engine control, which is then
called the "Engine and ECT ECU" .
TCC S
CONCEPTUAL DIAGRAM OF TCC S
This manual explains the TCCS type engine
control system . For details concerning other
systems (ECT, ABS, TEMS, etc .), please refer to
the training manual for each individual system .
OHP
1
In addition, this manual assumes that you have
mastered the contents of the manual for Step 2,
vol . 5 (EFI) . If you have not, please read that
manual carefully before beginning this one .
5

11
OUTLINE OF
TCCS - History of TCCS Engine Control Syste m
HISTORY OF TCCS ENGINE CONTROL SYSTE
M
The ECU used for conventional EFI in export
models beginning in 1979 was the analog circuit
type, which controlled the injection volume
based on the time required for a capacitor to be
charged and discharged .
The microcomputer-controlled type was added
beginning in 1981
. That was the beginning of the
engine control system using
TCCS . Now ,
however, the TCCS engine
control system not
only controls EFI, but also ESA, which controls
ignition timing ; ISC, which controls the idle
speed, and other such advanced systems ; as
well as the diagnostic, fail-safe, and back-up
functions .
CYL .
ARR .
ENGINE MODELS
1980 1985 1990 199 5
K series
(
4K-E)
-- ~
E series
( 3E-E) [2E-E, 4E-FE, 5E-FE ]
A series ( 4A-GE, 4AG-ZE )
[4A-FE, 5A-FE, 7A-FE ]
L4
S series ( 2S-E )
(1 S-i,
1S-E, 2S-E) 1 3S-FE, 5S-FE ,
3S-GE, 3S-GTE
]
R series ( 22R-E )
(22R-TE) [22R-E] ~
Y series ( 3Y-E )
[4Y-E ]
RZ series [1RZ-E, 2RZ-E, 2RZ-FE, 3RZ-FE 1
TZ series [2TZ-FE, 2TZ-FZE] ~
G series ( 1G-E)[1G-FE ]
(1G-GE)
----- ~
~
L6
M series (4M-E, 5M-E, 5M-GE
)
(5M-GE, 6M-GE, 7M-GE, 7M-GTE )
JZ series [2JZ-GE, 2JZ-GTE] ~
F series ( 3F-E) ~
FZ series [ 1 FZ-FE ]
V6
VZ series ( 2VZ-FE)[3VZ-E, 3VZ-FE, 5VZ-FE ]
MZ series [1 MZ-FE ]
V8 UZ series [1UZ-FE ]
INTAKE AIR SENSING DEVICE S
Vane type air flow meter -
Manifold pressure (vacuum) senso r
Optical Karman vortex type air flow mete r
Hot-wire type mass air flow meter -
1 : No longer in production models
I I
: Current product models
--- ~ : EFI (EFI control only
)
TCCS (EFI, ESA, ISC, Diagnosis,
etc )
6

OUTLINE OF TCCS - System Descriptio n
SYSTEM DESCRIPTIO N
The functions of the engine control system In addition, there are auxiliary engine control
include EFI, ESA, and ISC, which control basic devices on the engine, such as the OD cut-off con-
engine performance
; a diagnostic function, trol system, intake air control system, and others .
which is useful when repairs are made ; and fail- These functions
are all controlled by the Engine
safe and back-up functions, which operate when ECU .
any of these control systems malfunction .
Manifold pressure
sensor
Fuel pum
p
Knock senso r
Distributor
, (
and ignite r
Water temp . sensor
"E
Ignition switc h
Circuit opening relay
Engine EC U
Variable resistor
'
Check connecto r
Idle speed control
valv e
Intake air temp
. senso r
"Applicable only to General Country specification vehicles without oxygen sensor
.
LAYOUT OF ENGINE CONTROL SYSTEM COMPONENTS
(COROLLA 4A-FE ENGINE FOR EUROPE Apr
., 1992)
7

0 OUTLINE OF TCCS - System Descriptio n
1 . FUNCTIONS OF ENGINE CONTROL SYSTE M
EFI (ELECTRONIC FUEL INJECTION )
An electric fuel pump supplies sufficient fuel,
under a constant pressure, to the injectors .
These injectors inject a metered quantity of fuel
into the intake manifold in accordance with
signals from the Engine ECU .
The Engine ECU receives signals from various
sensors indicating changing engine operating
conditions such as :
• Manifold pressure (PIM) or intake air volume
(VS, KS or VG )
• Crankshaft angle (G)
• Engine speed (NE )
• Acceleration/deceleration (VTA)
• Coolant temperature (THW )
• Intake air temperature (THA)
etc .
ESA (ELECTRONIC SPARK ADVANCE )
The Engine ECU is programmed with data that
will ensure optimal ignition timing under any
and all operating conditions. Based on this data,
and on data provided by the sensors that
monitor various engine operating conditions,
such as those shown below, the Engine ECU
sends IGT (ignition timing) signals to the igniter
to trigger the spark at precisely the right instant .
• Crankshaft angle (G )
• Engine speed (NE )
• Manifold pressure ( PIM) or intake air volume
(VS, KS or VG
)
• Coolant temperature (THW)
etc .
Igniter and ignition coi l
These signals are utilized by the Engine ECU to
determine the injection duration necessary for
the optimal air-fuel ratio to suit the present
engine running conditions .
Fue l
+
Engine
EC U
Sensor s
OHP 3
Sensor
s
OHP
3
8

OUTLINE OF
TCCS - System Descriptio n
ISC (IDLE SPEED CONTROL )
The Engine ECU is programmed with target
engine speed values to respond to different
engine conditions such as
:
• Coolant temperature (THW)
• Air conditioner
on/off (A/C)
etc
.
Sensors transmit signals to the Engine ECU,
which, by means of the ISC valve, controls the
flow of air through the throttle valve bypass and
adjusts the idle speed to the target value
.
ISC valve
DIAGNOSTIC FUNCTIO N
The Engine ECU is constantly monitoring the
signals that are input to it from the various
sensors
. If it detects any malfunctions in the
input signals, the Engine ECU stores data on the
malfunction in its memory and lights the
"CHECK ENGINE"
lamp . When necessary, it
displays the malfunction
by lighting the "CHECK
ENGINE" lamp, displaying on a tester* or output-
ting a voltage signal
.
* OBD-II scan tool or TOYOTA
hand-held teste
r
"CHECK ENGINE" lamp
OHP 4
Sensor s
OHP 4
FAIL-SAFE FUNCTIO N
If the signals input to the Engine ECU are
abnormal, the Engine ECU switches to standard
values stored in its internal memory to control
the engine
. This makes it possible to control the
engine so as to continue more-or-less normal
vehicle operation .
BACK-UP FUNCTIO
N
Even if the Engine ECU itself becomes partially
inoperative, the back-up function can continue to
execute fuel injection and ignition timing
control
. This makes it possible to control the
engine so as to continue more-or-less normal
vehicle operation
.
OTHER CONTROL SYSTEM S
In some engines, the OD cut-off control system,
intake air control system, and some other aux-
iliary systems are also controlled by the Engine
ECU .
9

® OUTLINE OF TCCS - System Descriptio n
2 . CONSTRUCTION OF ENGINE CONTROL SYSTE M
BLOCK DIAGRA M
The engine control system can be broadly The sensors and actuators which form the basis
divided into three groups
: the sensors, the of an engine control system used in an engine
Engine ECU and the actuators
. with an oxygen sensor are shown below .
SENSOR S
MANIFOLD PRESSURE I I I I EF
I
SENSOR (D-TYPE EFI )
AIR FLOW METER*2
(L-TYPE EFI )
DISTRIBUTOR
----------------------------
• Crankshaft angle signa
l
• Engine speed signa l
WATER TEMP . SENSO R
INTAKE AIR TEMP . SENSO R
THROTTLE POSITION SENSO R
• Idling signa l
• Throttle position signa l
IGNITION SWITCH
(ST TERMINAL )
• Starting signa l
VEHICLE SPEED SENSO R
OXYGEN SENSO R
VARIABLE RESISTOR-
3
NEUTRAL START SWITC H
TAILLIGHT &
DEFOGGER RELAY S
AIR CONDITIONE R
KNOCK SENSO R
CHECK CONNECTOR
OXYGEN SENSOR HEATER
CONTRO L
OXYGEN SENSOR HEATE R
FUEL PUMP CONTRO L
CIRCUIT OPENING RELA Y
CHECK ENGINE LAMP
(Diagnostic code display )
PIM ~10
VS, KS
#20
or VG
G
N E
TH W
TH A
ID L
T A
ST A
SP
D
OX
VA F
NS W
EL S
A/
C
KN K
T E
TE
IG T
IG
F
IS C
RSC
ENGINE IRSO
I
ECU
H T
F C
W
BATT I 1 +1 3
BATTERY I I EFI MAIN RELA Y
* 1
* 2
*3
Actuators only related profoundly to the engine control are shown here
.
Although a D-type EFI is shown in the above figure and a L-type EFI sensor is also shown for reference .
Applicable only to General Country specification vehicles without oxygen sensor
.
ACTUATORS* '
NO .1 AND 3 INJECTOR S
NO .2 AND 4 INJECTOR S
ES A
IGNITE R
i
IGNITION COI L
i
DISTRIBUTO R
t
SPARK PLUG S
IS C
IDLE SPEED CONTROL VALV E
COROLLA
4A-FE ENGINE FOR EUROPE ( Apr ., 1992)
10

OUTLINE OF TCCS - System Descriptio
n
COMPONENTS AND FUNCTION S
The sensors, Engine ECU, and actuators, which
are the basis of the engine control system, are
shown in the following table, along with their
relationship with the main functions of the
engine control system, EFI, ESA and ISC .
®
REFERENCE
The signals used for each control may differ for
some engines .
COMPONENTS
SIG-
FUNCTIONS EFI ESA IS C
NAL S
Manifold pressure senso r
(
vacuum sensor)
(
D-type PIM
Senses intake manifold pressure .
EFI )
Air flow meter VS, KS
Senses intake air volume .
(L-type EFI) or V G
G
Senses crankshaft angle .
Distributor
NE
Senses engine speed .
Water temp . sensor THW
Senses coolant temperature .
Intake air temp . sensor
THA Senses intake air temperature .
Throttle position sensor
IDL Senses when throttle valve is fully closed
.
( on-off type)
PSW
Senses when throttle valve near fully open .
Throttle position sensor
IDL Senses when throttle valve is fully closed
.
Sensors
( linear type)
VTA Senses throttle valve opening angle
.
Ignition switch
STA Senses when ignition switch is start position
.
Vehicle speed sensor
SPD Senses vehicle speed .
Oxygen sensor
OX Senses oxygen density in exhaust gas
.
(02 sensor)
It is used to change the air-fuel ratio of the idl e
Variable resistor VAF mixture
.
Senses whether transmission is in "P" or "N"
,
Neutral start switch NSW
or in some other gear .
Taillight & defogger relays ELS Senses electrical load
.
Air conditioner
A/C
Senses whether air conditioner is on or off .
Knock sensor KNK Senses engine knocking
.
Determines injection duration and timing, igni -
tion timing, idle speed, etc., based upon dat
a
Engine ECU
from sensors and data stored in memory, an
d
sends appropriate signals to control actuators .
No .10
Injects fuel into intake manifold in accordanc e
Injectors
No .20
with signals from Engine ECU .
When IGT signals from Engine ECU go off ,
IGT primary
current to igniter is interrupted, an d
Actuators
Igniter
IGF
sparks are generated by spark plugs . Ignite r
then sends IGF signals to Engine ECU .
Controls idle speed by changing volume of ai
r
Idle speed control valve
ISC flowing through throttle valve bypass in accor
-
dance with signals from Engine ECU
.
11

a
OUTLINE OF
TCCS - System Descriptio n
3 . ENGINE CONTROL SYSTEM DIAGRA M
Neutral start
switch
~
~
Check connecto
r
Pressure regulator /
Injector
Circuit opening
rela y
Fuel pump
Speed
senso r
J
Combination
mete r
Fuel tank
Air
conditioner
amplifier
i f
Engine EC
U
Distributor and
ignite r
Knock
sensor
Variable
resistor *
Oxygen sensor
(02 sensor)
/
r
Water temp . sensor
Batter y
TW
C
*Applicable only to General Country specification vehicles without oxygen sensor
.
COROLLA 4A-FE
ENGINE FOR
EUROPE (Apr ., 1992)
Taillight relay
Defogger relay
r-o
~
Ignition switc h
CHECK
~ ENGINE "
~ lam p
12

ELECTRONIC CONTROL SYSTEM - Genera l
ELECTRONIC CONTROL SYSTE M
GENERA L
The engine control system can be divided into
three groups : sensors (and the signals output by
them), the ECU, and actuators . This section
describes only the sensor (signal) systems .
ECU functions are divided into EFI control, ESA
control, ISC control, diagnostic function, fail-safe
function, back-up function and others . Each of
these functions is covered in a separate section
of this manual .
Actuator functions are also covered in a
separate section .
41 1
The following table shows the specifications for
the 4A-FE engine . Information on sensors (and
their signals) marked with a circle in the
"APPENDIX" column is included in the
specifications for each engine in the APPENDIX
section (page 188) at the back of this manual .
Sensors (signals) covered in Step 2, vol . 5 (EFI),
are covered in outline form only in this manual .
If there is a circle in the "STEP 2(EFI)" column in
the following table, refer to the Step 2, vol . 5
(EFI), for a detailed explanation of the relevant
sensors (and their signals) .
SENSORS (SIGNALS)
PAG E
(THI S
MANUAL)
ITEM
REMARK
APPENDIX
STEP 2
(EFI
)
Engine without steppe r
motor type ISC valve
15 0
Power circuitry
Engine with steppe r
motor type ISC valve
1 6
VC circuitry
16
0
Ground circuitry
16
0
Manifold pressure senso r
(vacuum sensor)
17
0
Vane type
1 8
Air flow meter
Optcal Karman vorte x
type
2 1
Hot-wire type
21- 1
Throttle
On-off type
22
position sensor
Linear type
23 0
In-distributor type
24
G and NE signa l
enerators
Cam position sensor type 27
g
Separate type
28
Water temperature sensor
30
Intake air temperature
sensor 30
Oxygen sensor
Zirconia element type 31
With TW C
(02
sensor)
Titania element type 3 2
Lean mixture sensor 3 3
` Specifications for Carolla AE101 4A-FE engine (Apr
., 1992) (Continued
on next page )
13

ELECTRONIC CONTROL SYSTEM - Genera
l
SENSORS (SIGNALS)
PAG E
(THIS ITEM* REMARK
APPENDIX
STEP 2
MANUAL)
(EFI )
Reed switch type 3 4
Photocoupler type 3 4
Vehicle speed
Electromagnetic pickup
3 5
sensor
typ e
MRE (magnetic resistance
36 ~
element) typ e
STA (ignition switch) signal 38 J ~
NSW (neutral start switch 1 signal
38
A/C (air conditioner) signal 39
0
Electrical load signal 39
0
Fuel control switch or connector
40
EGR gas temperature sensor
40
r~
Californi a
specification model s
Variable resistor 41
C
Except with oxyge n
senso
r
Kick-down switch 42
Water temperature switch
42
Clutch switch
42
Knock sensor 43
With knockin g
correction for ES A
HAC (high-altitude compensation) sensor 44
Turbocharging pressure sensor 44
Stop lamp switch
45
Oil pressure switch
4 5
Throttle opening angle
4 5
signal s
Throttle opening angl
e
signals for TRC (traction 4 5
control) syste m
Cruise control system
4 6
communications signa l
TRC system
4 6
Communications
communications signa l
signals
ABS (anti-lock brak e
system) communications 4 6
signa l
Intercooler system
4 6
warning signa l
EHPS lelectro-hydrauli c
power steering) system 4 7
communications signa l
Engine speed signal 4 7
Diagnostic terminal (s) 4 7
• Specifications for Corolla AE101 4A-FE engine (Apr ., 1992 )
14