TOYOTA SUPRA 1986 Service Repair Manual

10
TROUBLESHOOTING
VOLTAGE CHECK
(a) Establish conditions in which voltage is present at the
check point.
Example:
± Ignition SW on
± Ignition SW and SW 1 on
± Ignition SW, SW 1 and Relay on (SW 2 off)
(b) Using a voltmeter, connect the negative lead to a good
ground point or negative battery terminal, and the
positive lead to the connector or component terminal.
This check can be done with a test light instead of a
voltmeter.
CONTINUITY AND RESISTANCE CHECK
(a) Disconnect the battery terminal or wire so there is no
voltage between the check points.
(b) Contact the two leads of an ohmmeter to each of the
check points.
If the circuit has diodes, reverse the two leads and check
again.
When contacting the negative lead to the diode positive side
and the positive lead to the negative side, there should be
continuity.
When contacting the two leads in reverse, there should be no
continuity.
(c) Use a volt/ohmmeter with high impedance (10 kW/V
minimum) for troubleshooting of the electrical circuit.

11
FINDING A SHORT CIRCUIT
(a) Remove the blown fuse and disconnect all loads of the
fuse.
(b) Connect a test light in place of the fuse.
(c) Establish conditions in which the test light comes on.
Example:
± Ignition SW on
± Ignition SW and SW 1 on
± Ignition SW, SW 1 and Relay on (Connect the
Relay) and SW 2 off (or Disconnect SW 2)
(d) Disconnect and reconnect the connectors while
watching the test light.
The short lies between the connector where the test
light stays lit and the connector where the light goes
out.
(e) Find the exact location of the short by lightly shaking
the problem wire along the body.
CAUTION:
(a) Do not open the cover or the case of the ECU unless
absolutely necessary. (If the IC terminals are
touched, the IC may be destroyed by static
electricity.)
(b) When replacing the internal mechanism (ECU part)
of the digital meter, be careful that no part of your
body or clothing comes in contact with the
terminals of leads from the IC, etc. of the
replacement part (spare part).
DISCONNECTION OF MALE AND FEMALE
CONNECTORS
To pull apart the connectors, pull on the connector itself, not the
wire harness.
HINT: Check to see what kind of connector you are disconnecting
before pulling apart.

12
TROUBLESHOOTING
HOW TO REPLACE TERMINAL
(with terminal retainer or secondary locking
device)
1. PREPARE THE SPECIAL TOOL
HINT: To remove the terminal from the connector, please
construct and use the special tool or like object shown
on the left.
2. DISCONNECT CONNECTOR
3. DISENGAGE THE SECONDARY LOCKING DEVICE OR
TERMINAL RETAINER.
(a) Locking device must be disengaged before the
terminal locking clip can be released and the terminal
removed from the connector.
(b) Use a special tool or the terminal pick to unlock the
secondary locking device or terminal retainer.
NOTICE:
Do not remove the terminal retainer from connector body.
For Non±Waterproof Type Connector
HINT: The needle insertion position varies according
to the connector's shape (number of terminals
etc.), so check the position before inserting it.
ªCase 1º
Raise the terminal retainer up to the temporary
lock position.
ªCase 2º
Open the secondary locking device.

13
For Waterproof Type Connector
HINT: Terminal retainer color is different
according to connector body.
Example:
Terminal Retainer
: Connector Body
Black or White : Gray
Black or White : Dark Gray
Gray or White : Black
ªCase 1º
Type where terminal retainer is pulled up
to the temporary lock position (Pull Type).
Insert the special tool into the terminal
retainer access hole ( Mark) and pull the
terminal retainer up to the temporary lock
position.
HINT: The needle insertion position varies
according to the connector's shape
(Number of terminals etc.), so check the
position before inserting it.
ªCase 2º
Type which cannot be pulled as far as
Power Lock insert the tool straight into the
access hole of terminal retainer as shown.

14
TROUBLESHOOTING
Push the terminal retainer down to the temporary lock
position.
(c) Release the locking lug from terminal and pull the
terminal out from rear.
4. INSTALL TERMINAL TO CONNECTOR
(a) Insert the terminal.
HINT:
1. Make sure the terminal is positioned correctly.
2. Insert the terminal until the locking lug locks firmly.
3. Insert the terminal with terminal retainer in the
temporary lock position.
(b) Push the secondary locking device or terminal retainer
in to the full lock position.
5. CONNECT CONNECTOR

15
TROUBLESHOOTING / ABBREVIATIONS
DISCONNECTION AND CONNECTION OF BOLT
TYPE CONNECTORS
For engine control module (engine and electronically controlled
transmission ECU) in this vehicle, connectors are used which
require a bolt built into the connector to be screwed down to
securely connect the connector.
1. Disconnect the connector
After completely loosening the bolt, the two parts of the
connector can be separated.
NOTICE:
Do not pull the wire harness when disconnecting the
connector.
2. Connect the connector
NOTICE:
Before connecting the connector, always check that the
terminals are not bent or damaged.
(a) Match the guide section of the male connector
correctly with the female connector, then press them
together.
(b) Tighten the bolt.
Make sure the connectors are completely connected,
by tightening the bolt until there is a clearance of less
than 1 mm (0.04 in.) between the bottom of male
connector and the end of female connector.
ABBREVIATIONS
The following abbreviations are used in this manual.
ABS = Anti±Lock Brake System O/D = Overdrive
A/C = Air Conditioning PPS = Progressive Power Steering
ACIS = Acoustic Control Induction System R/B = Relay Block
A/T = Automatic Transmission RH = Right±Hand
COMB. = Combination SFI = Sequential Multiport Fuel Injection
ECU = Electronic Control Unit SRS = Supplemental Restraint System
EFI = Electronic Fuel Injection SW = Switch
EGR = Exhaust Gas Recirculation TDCL = Total Diagnostic Communication Link
EVAP = Evaporative Emission TEMP. = Temperature
ISC = Idle Speed Control TRAC = Traction Control System
J/B = Junction Block VSV = Vacuum Switching Valve
LH = Left-Hand w/ = With
M/T = Manual Transmission w/o = Without
* The titles given inside the components are the names of the terminals (terminal codes) and are not treated
as being abbreviations.

15
ABBREVIATIONS
DISCONNECTION AND CONNECTION OF BOLT
TYPE CONNECTORS
For engine control module (engine and electronically controlled
transmission ECU) in this vehicle, connectors are used which
require a bolt built into the connector to be screwed down to
securely connect the connector.
1. Disconnect the connector
After completely loosening the bolt, the two parts of the
connector can be separated.
NOTICE:
Do not pull the wire harness when disconnecting the
connector.
2. Connect the connector
NOTICE:
Before connecting the connector, always check that the
terminals are not bent or damaged.
(a) Match the guide section of the male connector
correctly with the female connector, then press them
together.
(b) Tighten the bolt.
Make sure the connectors are completely connected,
by tightening the bolt until there is a clearance of less
than 1 mm (0.04 in.) between the bottom of male
connector and the end of female connector.
ABBREVIATIONS
The following abbreviations are used in this manual.
ABS = Anti±Lock Brake System O/D = Overdrive
A/C = Air Conditioning PPS = Progressive Power Steering
ACIS = Acoustic Control Induction System R/B = Relay Block
A/T = Automatic Transmission RH = Right±Hand
COMB. = Combination SFI = Sequential Multiport Fuel Injection
ECU = Electronic Control Unit SRS = Supplemental Restraint System
EFI = Electronic Fuel Injection SW = Switch
EGR = Exhaust Gas Recirculation TDCL = Total Diagnostic Communication Link
EVAP = Evaporative Emission TEMP. = Temperature
ISC = Idle Speed Control TRAC = Traction Control System
J/B = Junction Block VSV = Vacuum Switching Valve
LH = Left-Hand w/ = With
M/T = Manual Transmission w/o = Without
* The titles given inside the components are the names of the terminals (terminal codes) and are not treated
as being abbreviations.

METER, ANALOG
Current flow activates a magnetic
coil which causes a needle to
move, thereby providing a relative
display against a background
calibration. LED (LIGHT EMITTING DIODE)
Upon current flow, these diodes
emit light without producing the
heat of a comparable light. IGNITION COIL
Converts low±voltage DC current
into high±voltage ignition current
for firing the spark plugs. 1. SINGLE
FILAMENT
GROUND
The point at which wiring attaches
to the Body, thereby providing a
return path for an electrical circuit;
without a ground, current cannot
flow.Current flow causes a headlight
filament to heat up and emit light.
A headlight may have either a
single (1) filament or a double (2)
filament. BATTERY
Stores chemical energy and
converts it into electrical energy.
Provides DC current for the auto's
various electrical circuits.
CAPACITOR (Condenser)
A small holding unit for temporary
storage of electrical voltage.
CIRCUIT BREAKER
Basically a reusable fuse, a circuit
breaker will heat and open if too
much current flows through it. Some
units automatically reset when cool,
others must be manually reset.
DIODE
A semiconductor which allows
current flow in only one direction.
DIODE, ZENER
A diode which allows current flow
in one direction but blocks reverse
flow only up to a specific voltage.
Above that potential, it passes the
excess voltage. This acts as a
simple voltage regulator.
FUSE
A thin metal strip which burns
through when too much current
flows through it, thereby stopping
current flow and protecting a
circuit from damage.
FUSIBLE LINK
A heavy±gauge wire placed in
high amperage circuits which
burns through on overloads,
thereby protecting the circuit.
The numbers indicate the cross±
section surface area of the wires.HORN
An electric device which sounds a
loud audible signal.
LIGHT
Current flow through a filament
causes the filament to heat up
and emit light.
METER, DIGITAL
Current flow activates one or
many LED's, LCD's, or fluorescent
displays, which provide a relative
or digital display.
MOTOR
A power unit which converts
electrical energy into mechanical
energy, especially rotary motion. CIGARETTE LIGHTER
An electric resistance heating
element.
DISTRIBUTOR, IIA
Channels high±voltage current
from the ignition coil to the
individual spark plugs.2. DOUBLE
FILAMENT HEADLIGHTS
FUEL
(for High Current Fuse or
Fusible Link.)
(for Medium Current Fuse)
M
16
GLOSSARY OF TERMS AND SYMBOLS

17
1. NORMALLY
OPENOpens and
closes circuits,
thereby
stopping (1) or
allowing (2)
current flow.
RESISTOR
An electrical component with a
fixed resistance, placed in a circuit
to reduce voltage to a specific
value.
RESISTOR, TAPPED
A resistor which supplies two or
more different non adjustable
resistance values.
SENSOR (Thermistor)
A resistor which varies its
resistance with temperature.
SHORT PIN
Used to provide an unbroken
connection within a junction block.
SOLENOID
An electromagnetic coil which
forms a magnetic field when
current flows, to move a plunger,
etc.SWITCH, DOUBLE THROW
A switch which continuously
passes current through one set
of contacts or the other.
SWITCH,
IGNITION
A key operated switch with
several positions which allows
various circuits, particularly the
primary ignition circuit, to
become operational.
Wires are always
drawn as straight lines
on wiring diagrams.
Crossed wires (1)
without a black dot at
the junction are not
joined; crossed wires
(2) with a black dot or
octagonal (
) mark at
the junction are spliced
(joined) connections. RELAY, DOUBLE THROW
A relay which passes current
through one set of contacts or the
other.
SENSOR, ANALOG SPEED
Uses magnetic impulses to open
and close a switch to create a
signal for activation of other
components.TRANSISTOR
A solidstate device typically used
as an electronic relay; stops or
passes current depending on the
voltage applied at ªbase.º SWITCH, WIPER PARK
Automatically returns wipers to
the stop position when the wiper
switch is turned off. SWITCH, MANUAL SPEAKER
An electromechanical device
which creates sound waves from
current flow.
2. NORMALLY
CLOSED
RESISTOR, VARIABLE or
RHEOSTAT
A controllable resistor with a
variable rate of resistance.
Also called a potentiometer or
rheostat. 2. NORMALLY
OPEN RELAY
1. NORMALLY
CLOSEDBasically, an electrically
operated switch which may
be normally closed (1) or
open (2).
Current flow through a
small coil creates a
magnetic field which either
opens or closes an
attached switch.
(2) SPLICED WIRES
(1) NOT
CONNECTED

[Engine Compartment]
18
RELAY LOCATIONS
[Instrument Panel]