1995 TOYOTA SUPRA sensor

11. Care must be taken when jacking up and supporting the
vehicle. Be sure to lift and support the vehicle at the proper
locations (See page IN±36).
(a) If the vehicle is to be jacked up only at the front or rear
end, be sure to block the wheels at the opposite end in
order to ensure safety.
(b) After the vehicle is jacked up, be sure to support it on
stands. It is extremely dangerous to do any work on a
vehicle raised on a jack alone, even for a small job that
can be finished quickly.
12. Observe the following precautions to avoid damage to the
following parts:
(a) Do not open the cover or case of the ECU, ECM, PCM
or TCM unless absolutely necessary. (If the IC terminals
are touched, the IC may be destroyed by static
electricity.)
(b) To disconnect vacuum hoses, pull on the end, not the
middle of the hose.
(c) To pull apart electrical connectors, pull on the connector
itself, not the wires.
(d) Be careful not to drop electrical components, such as
sensors or relays. If they are dropped on a hard floor,
they should be replaced and not reused.
(e) When steam cleaning an engine, protect the distributor,
air filter, and VCV from water.
(f) Ne ve r use an imp a ct wre n ch to re mo ve or in sta ll
temperature switches or temperature sensors.
(g) When checking continuity at the wire connector, insert
the tester probe carefully to prevent terminals from
bending.
(h) When using a vacuum gauge, never force the hose onto
a connector that is too large. Use a step±down adapter
instead. Once the hose has been stretched, it may leak.
13. Tag hoses before disconnecting them:
(a) When disconnecting vacuum hoses, use tags to identify
how they should be reconnected.
(b) After completing a job, double check that the vacuum
hoses are properly connected. A label under the hood
shows the proper layout.
± INTRODUCTIONGENERAL REPAIR INSTRUCTIONSIN±7

When the negative (±) terminal cable is disconnected from
the battery, memory of the clock and audio systems will be
cancelled. So before starting work, make a record of the con-
tents memorized by the audio memory system. When work
is finished, reset the audio systems as before and adjust the
clock.
This vehicle has power tilt and power telescopic steering,
power seat, power outside rear view mirror and power shoul-
der belt anchorage, which are all equipped with memory
function, it is not possible to make a record of the memory
contents. So when the work is finished, therefore it will be
necessary to explain this fact to the customer, and ask the
customer to adjust the features and reset the memory.
To avoid erasing the memory of each memory system, never
use a back±up power supply from outside the vehicle.
3. Even in cases of a minor collision where the SRS does not
deploy, the steering wheel pad, front passenger airbag
assembly and front airbag sensors should be inspected (See
pages RS±10, 20, 30).
4. Never use SRS parts from another vehicle. When replacing
parts, replace them with new parts.
5. Before repairs, remove the airbag sensors if shocks are likely
to be applied to the sensors during repairs.
6. Never disassemble and repair the front airbag sensors,
center airbag sensor assembly, steering wheel pad or front
passenger airbag assembly in order to reuse it.
7. If the front airbag sensors, center airbag sensor assembly,
steering wheel pad, front passenger airbag assembly or seat
belt pretensioners have been dropped, or if there are cracks,
dents or other defects in the case, bracket or connector,
replace them with new ones.
8. Do not expose the front airbag sensors, center airbag sensor
assembly, steering wheel pad, front passenger airbag
assembly or seat belt pretensioners directly to hot air or
flames.
9. Use a volt/ohmmeter with high impedance (10 k
/V
minimum) for troubleshooting of the electrical circuit.
10. Information labels are attached to the periphery of the SRS
components. Follow the instructions on the notices.
11. After work on the supplemental restraint system is
completed, perform the SRS warning light check (See page
RS±44).
± INTRODUCTIONPRECAUTIONIN±11

Front Airbag Sensor
1. Never reuse the front airbag sensors involved in a collision
that activated the supplemental restraint system. (Replace
both left and right airbag sensors.)
2. Install the front airbag sensor with the arrow on the sensor
facing toward the front of the vehicle.
3. The front airbag sensor set bolts have been anti±rust treated.
When the sensor is removed, always replace the set bolts
with new ones.
4. The front airbag sensor is equipped with an electrical
connection check mechanism. Be sure to lock this
mechanism securely when connecting the connector. If the
connector is not securely locked, a malfunction code will be
detected by the diagnosis system (See page RS±7).
Spiral Cable (in Combination Switch)
The steering wheel must be fitted correctly to the steering col-
umn with the spiral cable at the neutral position, otherwise
cable disconnection and other troubles may result. Refer to
page SR±14 of this manual concerning correct steering
wheel installation.
Steering Wheel Pad (with Airbag)
1. When removing the steering wheel pad or handling a new
steering wheel pad, it should be placed with the pad top
surface facing up.
In this case, the twin±lock type connector lock lever should
be in the locked state and care should be taken to place it so
the connector will not be damaged. In addition do not store
a steering wheel pad on top of another one. Storing the pad
with its metallic surface up may lead to a serious accident if
the airbag inflates for some reason.
2. Never measure the resistance of the airbag squib. (This
may cause the airbag to deploy, which is very
dangerous.)
3. Grease should not be applied to the steering wheel pad and
the pad should not be cleaned with detergents of any kind.
4. Store the steering wheel pad where the ambient temperature
remains below 93°C (200°F), without high humidity and
away from electrical noise. IN±12
± INTRODUCTIONPRECAUTION

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

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

[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

[3] SYMPTOM SIMULATION
The most difficult case in troubleshooting is when there are no problem symptoms occurring. In such cases, a
thorough customer problem analysis must be carried out, then simulate the same or similar conditions and envi-
ronment in which the problem occurred in the customer's vehicle. No matter how much experience a technician
has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem symptoms he will
tend to overlook something important in the repair operation and make a wrong guess somewhere, which will
only lead to a standstill. For example, for a problem which only occurs when the engine is cold, or for a problem
which occurs due to vibration caused by the road during driving, etc., the problem can never be determined so
long as the symptoms are confirmed with the engine hot condition or the vehicle at a standstill. Since vibration,
heat or water penetration (moisture) are likely causes for problems which are difficult to reproduce, the symptom
simulation tests introduced here are effective measures in that the external causes are applied to the vehicle
in a stopped condition.
Important Points in the Symptom Simulation Test
In the symptom simulation test, the problem symptoms should of course be confirmed, but the problem area
or parts must also be found out. To do this, narrow down the possible problem circuits according to the symptoms
before starting this test and connect a tester beforehand. After that, carry out the symptom simulation test, judg-
ing whether the circuit being tested is defective or normal and also confirming the problem symptoms at the
same time. Refer to the matrix chart of problem symptoms for each system to narrow down the possible causes
of the symptom.
VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
Slightly shake the connector vertically and horizontally.
WIRE HARNESS
Slightly shake the connector vertically and horizontally
.
The connector joint, fulcrum of the vibration, and body
through portion are the major areas to be checked thor-
oughly.
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the sen-
sor considered to be the problem cause and check if the
malfunction occurs.
HINT: Applying strong vibration to relays may result in
open relays. IN±24
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS

HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION
PROCEDURE
1. For troubleshooting, diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages.
2. When all the component parts, wire harnesses and connectors of each circuit except the ECU are found
to be normal in troubleshooting, then it is determined that the problem is in the ECU.
Accordingly, if diagnosis is performed without the problem symptoms occurring, the instruction will be to
check and replace the ECU, even if the problem is not in the ECU. So, always confirm that the problem
symptoms are occurring, or proceed with inspection while using the symptom simulation method.
3. The instructions ºCheck wire harness and connectorº and ºCheck and replace ECUº which appear in the
inspection procedure, are common and applicable to all diagnostic trouble codes. Follow the procedure
outlined below whenever these instructions appear.
Check Wire Harness and Connector
The problem in the wire harness or connector is an open circuit or a short circuit.
OPEN CIRCUIT:
This could be due to a disconnected wire harness, faulty contact in the connector, a connector terminal pulled
out, etc.
HINT:
1. It is rarely the case that a wire is broken in the middle of it. Most cases occur at the connector. In particular,
carefully check the connectors of sensors and actuators.
2. Faulty contact could be due to rusting of the connector terminals, to foreign materials entering terminals
or a drop in the contact pressure between the male and female terminals of the connector. Simply
disconnecting and reconnecting the connectors once changes the condition of the connection and may
result in a return to normal operation.
Therefore, in troubleshooting, if no abnormality is found in the wire harness and connector check, but the
problem disappears after the check, then the cause is considered to be in the wire harness or connectors.
SHORT CIRCUIT:
This could be due to a short circuit between the wire harness and the body ground or to a short inside the switch,
etc.
HINT:
wWhen there is a short between the wire harness and body ground, check thoroughly whether the wire
harness is caught in the body or is clamped properly. IN±30
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS