TOYOTA SUPRA 1995 Service Repair Manual

5. When using electric welding, first disconnect the airbag
connector (yellow color and 2 pins) installed on the glove
compartment finish plate at the left side of the glove
compartment before starting work.
6. When disposing of a vehicle or the airbag assembly
alone, the airbag should be deployed using an SST
before disposal (See page RS±25).
Perform the operation in a safe place away from electri-
cal noise.
Center Airbag Sensor Assembly
1. Never reuse the center airbag sensor assembly involved in
a collision when the SRS has deployed.
2. The connectors to the center airbag sensor assembly should
be connected or disconnected with the sensor mounted on
the floor. If the connectors are connected or disconnected
while the center airbag sensor assembly is not mounted to
the floor, it could cause undesired ignition of the
supplemental restraint system.
3. Work must be started after 90 seconds from the time the
ignition switch is turned to the LOCK position and the
negative (±) terminal cable is disconnected from the battery,
even if only loosening the set bolts of the center airbag
sensor assembly. IN±14
± INTRODUCTIONPRECAUTION

Wire Harness and Connector
The SRS wire harness is integrated with the cowl wire har-
ness assembly and floor wire harness assembly. The wires
for the SRS wire harness are encased in a yellow corrugated
tube. All the connectors for the system are also a standard
yellow color. If the SRS wire harness becomes disconnected
or the connector becomes broken due to an accident, etc.,
repair or replace it as shown on page RS±36.
FOR VEHICLES EQUIPPED WITH A CATALYTIC CONVERTER
CAUTION: If large amounts of unburned gasoline flow into the converter, it may overheat and create a fire
hazard. To prevent this, observe the following precautions and explain them to your customer.
1. Use only unleaded gasoline.
2. Avoid prolonged idling.
Avoid running the engine at idle speed for more than 20 minutes.
3. Avoid spark jump test.
(a) Perform spark jump test only when absolutely necessary. Perform this test as rapidly as possible.
(b) While testing, never race the engine.
4. Avoid prolonged engine compression measurement.
Engine compression tests must be done as rapidly as possible.
5. Do not run engine when fuel tank is nearly empty.
This may cause the engine to misfire and create an extra load on the converter.
6. Avoid coasting with ignition turned off and prolonged braking.
7. Do not dispose of used catalyst along with parts contaminated with gasoline or oil.
± INTRODUCTIONPRECAUTIONIN±15

FOR VEHICLES EQUIPPED WITH
TRACTION CONTROL (TRAC) SYSTEM
When using a rear wheel two±wheel drum tester such as a
speedometer tester or chassis dynamometer, etc., or jacking
up the rear wheels and driving the wheels, always push in the
TRAC cut (ºTRAC OFFº) switch and turn the TRAC system
OFF.
CONFIRM TRAC SYSTEM IS OFF
1. Press the TRAC cut (ºTRAC OFFº) switch.
2. Check that the TRAC OFF indicator light comes on when the
TRAC system is turned off by the TRAC cut switch.
HINT: The TRAC indicator light should always operate right
after the engine is restarted.
3. Begin measurements.
4. Press the TRAC cut switch again to change the TRAC to
operative and check that the TRAC OFF indicator light goes
off.
HINT: The TRAC indicator light blinks when the TRAC system
is operative. IN±16
± INTRODUCTIONPRECAUTION

INSPECTION AND ADJUSTMENT OF
JOINT ANGLE DURING REMOVAL AND
INSTALLATION OF PROPELLER SHAFT
When performing operations which involve the removal and
installation of the propeller shaft, always check the joint
angle. Make adjustments if necessary (See page PR±18).
± INTRODUCTIONPRECAUTIONIN±17

IF VEHICLE IS EQUIPPED WITH MOBILE
COMMUNICATION SYSTEM
For vehicles with mobile communication systems such as
two±way radios and cellular telephones, observe the follow-
ing precautions.
(1) Install the antenna as far as possible away from the ECM,
ECU and sensors of the vehicle's electronic system.
(2) Install the antenna feeder at least 20 cm (7.87 in.) away from
the ECM, ECU and sensors of the vehicle's electronics
systems. For details about ECM, ECU and sensors locations,
refer to the section on the applicable component.
(3) Do not wind the antenna feeder together with the other
wiring. As much as possible, also avoid running the antenna
feeder parallel with other wire harnesses.
(4) Confirm that the antenna and feeder are correctly adjusted.
(5) Do not install powerful mobile communications system. IN±18
± INTRODUCTIONPRECAUTION

HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
A large number of ECU controlled systems are used in the TOYOTA SUPRA. In general, the ECU controlled
system is considered to be a very intricate system requiring a high level of technical knowledge and expert skill
to troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, troubleshooting of
these systems is not complex. If you have adequate understanding of the system and a basic knowledge of
electricity, accurate diagnosis and necessary repair can be performed to locate and fix the problem. This manual
is designed through emphasis of the above standpoint to help service technicians perform accurate and effec-
tive troubleshooting, and is compiled for the following major ECU controlled systems:
 Repair Manual System Page
 
Vol 1
 
1
 2JZ±GE Engine EG±381
 Vol. 1  1. 2JZ±GTE Engine EG±487
  
2
 A340E (2JZ±GE) Automatic Transmission AT1±31   2. A340E (2JZ±GTE) Automatic Transmission AT1±31 
 
 
  3.
 
 Anti±Lock Brake
 
 BR±51
 Vol 2  4. Traction Control BR±123
 Vol. 2  5. Supplemental Restraint System RS±41
   6. Theft Deterrent and Door Lock System BE±142
   7. Cruise Control BE±163
   8. Air Conditioning AC±13
The troubleshooting procedure and how to make use of it are described on the following pages.
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN±19

HOW TO PROCEED WITH TROUBLESHOOTING
Carry out troubleshooting in accordance with the procedure on the following page. Here, only the basic proce-
dure is shown. Details are provided in each section, showing the most effective methods for each circuit. Confirm
the troubleshooting procedures first for the relevant circuit before beginning troubleshooting of that circuit.
Vehicle Brought to Workshop
Customer Problem
Analysis
Symptom Confirmation
and Diagnostic Trouble
Code Check
Diagnostic Trouble Code
Chart
Symptom Simulation
Matrix chart of Problem
Symptoms
Circuit Inspection or Parts
Inspection
Confirmation Test
Repair
End
After completing repairs, confirm that the problem
has been eliminated.
(If the problem is not reproduced, perform the con-
firmation test under the same conditions and in the
same environment as when it occurred for the first
time.)
Check and repair the affected system or part in ac-
cordance with the instructions in Step [6].
Check the results obtained in Step [2], then confirm
the inspection procedure for the system or the part
which should be checked using the diagnostic
trouble code chart or the matrix chart of problem
symptoms.
Confirm the symptoms and the problem conditions,
and check the diagnostic trouble codes.
(When the problem symptoms do not appear dur-
ing confirmation, use the symptom simulation
method described later on.)
Ask the customer about the conditions and the en-
vironment when the problem occurred. IN±20
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS

[1] CUSTOMER PROBLEM ANALYSIS
In troubleshooting, the problem symptoms must be confirmed accurately and all preconceptions must be
cleared away in order to give an accurate judgment. To ascertain just what the problem symptoms are, it is ex-
tremely important to ask the customer about the problem and the conditions at the time it occurred.
Important Points in the Problem Analysis
The following 5 items are important points in the problem analysis. Past problems which are thought to be unre-
lated and the repair history, etc. may also help in some cases, so as much information as possible should be
gathered and its relationship with the problem symptoms should be correctly ascertained for reference in trou-
bleshooting. A customer problem analysis table is provided in the troubleshooting section for each system for
your use.
Important Points in the Customer Problem Analysis
wWhat ..................... Vehicle model, system name
wWhen ..................... Date, time, occurrence frequency
wWhere ..................... Road conditions
wUnder what conditions?.............. Running conditions, driving conditions, weather conditions
wHow did it happen? ..................... Problem symptoms
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN±21

[2] SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the TOYOTA SUPRA fulfills various functions. The first function is the Diagnostic
Trouble Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory
at the time of occurrence, to be output by the technician during troubleshooting. Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly. The air condition-
ing system has an Actuator Check function whereby the ECU automatically operates the actuators of the damp-
er and blowermotor, etc. to check the operation. By using these check functions, the problem areas can be nar-
rowed down quickly and troubleshooting can be performed effectively. Diagnostic functions are incorporated
in the following systems in the TOYOTA SUPRA.
 
 System
 
 
Diagnostic Trouble
Code Check 
 
Input Signal Check
(Sensor Check) 
 
Other Diagnosis
Function
 
 
 
 
 
 
Engine
Automatic Transmission
Anti±Lock Brake
Traction Control (Option)
Supplemental Restraint System
Cruise Control
Air Conditioning 
 
 
 
 
 
O (with Test Mode)
O (with Test Mode)
O
O
O
O
O 
 
 
 
 
 
O
O
O
O
O
O 
 
 
 
 
 Actuator Check
In diagnostic trouble code check, it is very important to determine whether the problem indicated by the diagnos-
tic trouble code is still occurring or occurred in the past but returned to normal at present. In addition, it must
be checked in the problem symptom check whether the malfunction indicated by the diagnostic trouble code
is directly related to the problem symptom or not. For this reason, the diagnostic trouble codes should be
checked before and after the symptom confirmation to determine the current conditions, as shown in the table
below. If this is not done, it may, depending on the case, result in unnecessary troubleshooting for normally oper-
ating systems, thus making it more difficult to locate the problem, or in repairs not pertinent to the problem.
Therefore, always follow the procedure in correct order and perform the diagnostic trouble code check.
DIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
 
 
 
Diagnostic Trouble
Code Check (Make a
note of and then clear) 
 
 
Confirmation of
symptoms 
 
 
Diagnostic Trouble
Code Check 
 
 
Problem Condition
 
 
Diagnostic
Trouble Code
Display 
 
Problem symptoms
exist 
 
Same Diagnostic
trouble code is dis-
played 
 
Problem is still occurring in the diagnos-
tic circuit
 
 
 
 
 
%
 
 
 
 
 
 
 
 
 
 
Normal code is dis-
played 
 
 
 
 
The problem is still occurring in a place
other than in the diagnostic circuit. (The
diagnostic trouble code displayed first is
either for a past problem or it is a sec-
ondary problem.)
 
 %
 
 
No problem
symptoms exist 
 
 
 
The problem occurred in the diagnostic
circuit in the past.
 
 
Normal Code Display
%
 
 
Problem symptoms
exist 
 
Normal code is dis-
played 
 
The problem is still occurring in a place
other than in the diagnostic circuit.
 
 %
 
 
No problem
symptoms exist 
 
Normal code is dis-
played 
 
The problem occurred in a place other
than in the diagnostic circuit in the past.
IN±22± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS

Taking into account the above points, a flow chart showing how to proceed with troubleshooting using the diag-
nostic trouble code check is shown below. This flow chart shows how to utilize the diagnostic trouble code check
effectively, then by carefully checking the results, indicates how to proceed either to diagnostic trouble code
troubleshooting or to troubleshooting of problem symptoms.
Diagnostic trouble code check
Making a note of and clearing of the diagnostic trouble codes displayed
Symptom confirmation
No problem symptoms
existProblem symptoms
exist
Simulation test using the symptom
simulation methods
Diagnostic trouble code check

Diagnostic trouble code
displayed

Problem symptoms exist
Normal code displayed

Problem symptoms exist
Normal code displayed

No Problem symptoms
exist
Troubleshooting of problem
indicated by diagnostic rouble
codeTroubleshooting of each
problem symptom
System Normal
If a diagnostic trouble code was dis-
played in the initial diagnostic trouble
code check, it indicates that the trouble
may have occurred in a wire harness or
connector in that circuit in the past.
Therefore, check the wire harness and
connectors (See page
IN±30).
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN±23