1986 TOYOTA SUPRA Service Repair Manual

* The system shown here is an EXAMPLE ONLY. It is different to the actual circuit shown in the SYSTEM CIRCUITS SECTION.
POWER SOURCE (Current Flow Chart)
The chart below shows the route by which current flows from the battery to each electrical source (Fusible Link, Circuit
Breaker, Fuse, etc.) and other parts.
The next page and following pages show the parts to which each electrical source outputs current.
POWER SOURCE
8
HOW TO USE THIS MANUAL
The ªCurrent Flow Chartº section, describes which parts each power source (fuses, fusible links, and circuit breakers)
transmits current to. In the Power Source circuit diagram, the conditions when battery power is supplied to each system are
explained. Since all System Circuit diagrams start from the power source, the power source system must be fully understood.

* The system shown here is an EXAMPLE ONLY. It is different to the actual circuit shown in the SYSTEM CIRCUITS SECTION.
GROUND POINTS
9
The ground points circuit diagram shows the connections from all major parts to the respective ground points. When
troubleshooting a faulty ground point, checking the system circuits which use a common ground may help you identify the
problem ground quickly. The relationship between ground points ( , , and shown below) can also be
checked this way.

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.