1995 TOYOTA SUPRA ECU

3. USE OF PROPER O±RINGS AND SEALS
O±rings and seals used for conventional CFC12 air condi-
tioning systems cannot be used for HFC134a air conditioning
systems.
Always use genuine Toyota HFC134a system O±rings and
seals for HFC134a air conditioning systems.
If O±rings and/or seals for CFC12 air conditioning systems
are used by mistake in the connections of an HFC134a air
conditioning system, the O±ring and seals will foam and swell
resulting in leakage of refrigerant.
4. TIGHTEN CONNECTING PARTS SECURELY
Securely tighten the connecting parts to prevent leaking of
refrigerant gas.
wApply a few drops of compressor oil to O±ring fittings for
easy tightening and to prevent leaking of refrigerant
gas.
CAUTION: Apply only ND±OIL 8 compressor oil.
wTighten the nuts using 2 wrenches to avoid twisting the
tube.
wTighten the O±ring fittings or the bolted type fittings to
the specified torque.
5. INSERT PLUG IMMEDIATELY IN DISCONNECTED PARTS
Insert a plug immediately in the disconnected parts to pre-
vent the ingress of moisture and dust.
6. DO NOT REMOVE PLUG FROM NEW PARTS UNTIL
IMMEDIATELY BEFORE INSTALLATION
7. DISCHARGE GAS IN NEW COMPRESSOR FROM
CHARGING VALVE BEFORE INSTALLING IT
If the gas in the new compressor is not discharged first, com-
pressor oil will spray out with gas when the plug is removed.
± AIR CONDITIONING SYSTEMGENERAL DESCRIPTIONAC±3

INDICATOR CHECK
1. Turn the ignition switch on while pressing the air conditioning
control AUTO switch and R/F SW simultaneously.
2. Check that all the indicators light up and go off at 1
second intervals 4 times in succession.
HINT:
wAfter the indicator check is ended, the diagnostic sensor
check begins automatically.
wPress the OFF switch when cancelling the check mode.
DIAGNOSTIC SENSOR CHECK
1. Perform an indicator check. After the indicator check is
completed, the system enters the diagnostic sensor check
mode automatically.
2. Check the LED blinking on the panel. Refer to the list of codes
on page AC±20 when translating the trouble code from the
LED blinking.
If the slower display is desired, press the RDEF switch and
change it to step operation. Each time the RDEF switch is
pressed, the blinking LED changes by 1 step.
CLEARING TROUBLE CODES' MEMORY
Method 1:
1. Pull out the ECU±B fuse in Junction Block No. 1 for 10 sec.
or longer to clear the trouble codes' memory.
2. After reinserting the fuse, check that the normal code is
output.
Method 2:
Press the RDEF switch while pushing the A/C switch during
the sensor check mode. AC±18
± AIR CONDITIONING SYSTEMTROUBLESHOOTING

INSPECTION PROCEDURE
Remove the A/C amplifier with connector still con-
ected.
Measure voltage between terminal + B of air condi-
tioner control assembly connector and body ground.
Voltage: Battery positive voltage
Proceed to next circuit inspection shown on matrix
chart (See page AC±26).

Remove ECU±B fuse from J/B No. 1.
Check continuity of ECU±B fuse.
Continuity
Check ECU±B fuse.
Check for short in all the harness and compo-
nents to the ECU±B fuse (See attached wiring
diagram).
Check voltage between terminal +B of A/C amplifier connector and
body ground.
Check and repair harness and connector between
A/C amplifier and battery.
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±53

INTRODUCTIONGENERAL REPAIR INSTRUCTIONS -
IN-4
GENERAL REPAIR INSTRUCTIONS
1. Use fender, seat and floor covers to keep the vehicle
clean and prevent damage.
2. During disassembly, keep parts in the appropriate order
to facilitate reassembly.
3. Observe the following:
(a) Before performing electrical work, disconnect the
negative cable from the battery terminal.
(b) If it is necessary to disconnect the battery for inspec-
tion or repair, always disconnect the cable from the
negative (-) terminal which is grounded to the ve-
hicle body.
(c) To prevent damage to the battery terminal post, loos-
en the terminal nut and raise the cable straight up
without twisting or prying it.
(d) Clean the battery terminal posts and cable terminals
with a clean shop rag. Do not scrape them with a file
or other abrasive objects.
(e) Install the cable terminal to the battery post with the
nut loose, and tighten the nut after installation. Do
not use a hammer to tap the terminal onto the post.
(f) Be sure the cover for the positive (+) terminal is prop-
erly in place.
4. Check hose and wiring connectors to make sure that they
are secure and correct.
5. Non-reusable parts
(a) Always replace cotter pins, gaskets, O-rings and oil
seals etc. with new ones.
(b) Non-reusable parts are indicated in the component
illustrations by the ºº symbol.
6. Precoated parts
Precoated parts are bolts and nuts, etc. that are coated
with a seal lock adhesive at the factory.
(a) If a precoated part is retightened, loosened or
caused to move in any way, it must be recoated with
the specified adhesive.
(b) When reusing precoated parts, clean off the old
adhesive and dry with compressed air. Then applyIN022-02

INTRODUCTIONGLOSSARY OF SAE AND TOYOTA TERMS -
IN-7
GLOSSARY OF SAE AND TOYOTA TERMS
This glossary lists all SAE-J1930 terms and abbreviations used in this manual in compliance with SAE
recommendations, as well as their Toyota equivalents.
SAE
ABBREVIATIONSSAE TERMSTOYOTA TERMS
( )--ABBREVIATIONS
A/CAir ConditioningAir Conditioner
ACLAir CleanerAir Cleaner
AIRSecondary Air InjectionAir Injection (AI)
APAccelerator Pedal-
B+Battery Positive Voltage+B, Battery Voltage
BAROBarometric Pressure-
CACCharge Air CoolerIntercooler
CARBCarburetorCarburetor
CFIContinuous Fuel Injection-
CKPCrankshaft PositionCrank Angle
CLClosed LoopClosed Loop
CMPCamshaft PositionCam Angle
CPPClutch Pedal Position-
CTOXContinuous Trap Oxidizer-
CTPClosed Throttle Position-
DFIDirect Fuel Injection (Diesel)Direct Injection (DI)
DIDistributor Ignition-
DLC1
DLC2
DLC3Data Link Connector 1
Data Link Connector 2
Data Link Connector 31: Check Connector
2: Toyota Diagnosis Communication Link (TDCL)
3: OBD II Diagnostic Connector
DTCDiagnostic Trouble CodeDiagnostic Code
DTMDiagnostic Test Mode-
ECLEngine Control Level-
ECMEngine Control ModuleEngine ECU (Electronic Control Unit)
ECTEngine Coolant TemperatureCoolant Temperature, Water Temperature (THW)
EEPROMElectrically Erasable Programmable Read Only
MemoryElectrically Erasable Programmable Read Only Memory
(EEPROM),
Erasable Programmable Read Only Memory(EPROM)
EFEEarly Fuel EvaporationCold Mixture Heater (CMH), Heat Control Valve (HCV)
EGRExhaust Gas RecirculationExhaust Gas Recirculation (EGR)
EIElectronic IgnitionToyota Distributorless Ignition (TDI)
EMEngine ModificationEngine Modification (EM)
EPROMErasable Programmable Read Only MemoryProgrammable Read Only Memory (PROM)
EVAPEvaporative EmissionEvaporative Emission Control (EVAP)
FCFan Control-
FEEPROMFlash Electrically Erasable Programmable
Read Only Memory-
FEPROMFlash Erasable Programmable Read Only Memory-
FFFlexible Fuel-
FPFuel PumpFuel Pump
GENGeneratorAlternator
GNDGroundGround (GND)
HO2SHeated Oxygen SensorHeated Oxygen Sensor (HO2S)
IN016-02

INTRODUCTIONGLOSSARY OF SAE AND TOYOTA TERMS -
IN-8
IACIdle Air ControlIdle Speed Control (ISC)
IATIntake Air TemperatureIntake or Inlet Air Temperature
ICMIgnition Control Module-
IFIIndirect Fuel InjectionIndirect Injection
IFSInertia Fuel-Shutoff-
ISCIdle Speed Control-
KSKnock SensorKnock Sensor
MAFMass Air FlowAir Flow Meter
MAPManifold Absolute PressureManifold Pressure
Intake Vacuum
MCMixture Control
Electric Bleed Air Control Valve (EBCV)
Mixture Control Valve (MCV)
Electric Air Control Valve (EACV)
MDPManifold Differential Pressure-
MFIMultiport Fuel InjectionElectronic Fuel Injection (EFI)
MILMalfunction Indicator LampCheck Engine Light
MSTManifold Surface Temperature-
MVZManifold Vacuum Zone-
NVRAMNon-V olatile Random Access Memory-
O2SOxygen SensorOxygen Sensor, O2 Sensor (O2S)
OBDOn-Board DiagnosticOn-Board Diagnostic (OBD)
OCOxidation Catalytic ConverterOxidation Catalyst Converter (OC), CCo
OPOpen LoopOpen Loop
PAIRPulsed Secondary Air InjectionAir Suction (AS)
PCMPowertrain Control Module-
PNPPark/Neutral Position-
PROMProgrammable Read Only Memory-
PSPPower Steering Pressure-
PTOXPeriodic Trap OxidizerDiesel Particulate Filter (DPF)
Diesel Particulate Trap (DPT)
RAMRandom Access MemoryRandom Access Memory (RAM)
RMRelay Module-
ROMRead Only MemoryRead Only Memory (ROM)
RPMEngine SpeedEngine Speed
SCSuperchargerSupercharger
SCBSupercharger Bypass-
SFISequential Multiport Fuel InjectionElectronic Fuel Injection (EFI), Sequential Injection
SPLSmoke Puff Limiter-
SRIService Reminder Indicator-
SRTSystem Readiness Test-
STScan Tool-
TBThrottle BodyThrottle Body
TBIThrottle Body Fuel InjectionSingle Point Injection
Central Fuel Injection (Ci)
TCTurbochargerTurbocharger
TCCTorque Converter ClutchTorque Converter
TCMTransmission Control ModuleTransmission ECU (Electronic Control Unit)
TPThrottle PositionThrottle Position
TRTransmission Range-

ELECTRONIC CONTROL SYSTEM
The electronic control system, which controls the shift points and the operation of the lock±up clutch, is
composed of the following three parts:
1. Sensors
These sensors sense the vehicle speed, throttle opening and other conditions and send this data to the
ECM in the form of electrical signals.
2. ECM
The ECM determines the shift and lock±up timing based upon the signals from sensors, and controls the
solenoid valves of the hydraulic control unit accordingly.
3. Actuators
These are three solenoid valves that control hydraulic pressure acting on the hydraulic valves to control
shifting and lock±up timing.
SENSORSECM
DRIVING PATTERN
SELECTOR
PARK/NEUTRAL
POSITIOIN SWITCH
THROTTLE POSITIOIN
SENSOR
VEHICLE SPEED
SENSOR
STOP LIGHT SWITCH
O/D MAIN SWITCH
CRUISE CONTROL
ECU
ENGINE COOLANT TEM-
PERATURE SENSOR
A/T FLUID
TEMPERATURE SENSOR
Back±up system
Self±diagnostic
system
Control of lock±
up timing
Control of shift
timing
ACTUATORS
NO. 1
SOLENOID VALVE
NO. 2
SOLENOID VALVE
LOCK±UP
SOLENOID VALVE
O/D OFF INDICA-
TOR LIGHT
± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONOPERATIONAT1±7

FUNCTION OF ECU
w Control of Shifting Timing
The ECM has programmed into its memory the optimum shift pattern for each shift lever position (D, 2, L
position) and driving mode (Normal or Manual).
Based on the appropriate shift pattern, the ECM turns No.1 and No.2 solenoid valves on or off in accor-
dance with the vehicle speed signal from the vehicle speed sensor and the throttle opening signal from the
throttle position sensor. In this manner, the ECM operates each shift valve, opening or closing the fluid pas-
sages to the clutches and brakes to permit up±shift or down±shift of the transmission.
HINT: The electronic control system provides shift timing and lock±up control only while the vehicle is travel-
ing forward. In REVERSE, PARK, and NEUTRAL, the transmission is mechanically, not electronically con-
trolled.
w Control of Overdrive
Driving in overdrive is possible if the O/D main switch is on and the shift lever is in the D position. However,
when the vehicle is being driven using the cruise control system (CCS), if the actual vehicle speed drops
to about 4 km/h (2 mph) below the set speed while the vehicle is running in overdrive, the CCS ECU sends
a signal to the ECM to release the overdrive and prevent the transmission from shifting back into overdrive
until the actual vehicle speed reaches the speed set in the CCS memory.
On this model, if the engine coolant temperature falls below 60°C (140°F), the ECM sends a signal to the
ECM, preventing the transmission from up±shifting into overdrive.
w Control of Lock±Up System
The ECM has programmed in its memory a lock±up clutch operation pattern for each driving mode (Normal
of Manual). Based on this lock±up pattern, the ECM turns lock±up solenoid valve on or off in accordance
with the vehicle speed signals received from the vehicle speed sensor and the throttle opening signals from
the throttle position sensor.
Depending on whether lock±up solenoid valve is on or off, the lock±up relay valve performs changeover
of the fluid passages for the converter pressure acting on the torque converter clutch to engage or disen-
gage the lock±up clutch.
Mandatory Cancellation of Lock±Up System:
If any of the following conditions exist, the ECM turns off lock±up solenoid valve to disengage the lock±up
clutch.
1) The brake light switch comes on (during braking).
2) The IDL points of the throttle position sensor close (throttle valve fully closed).
3) The vehicle speed drops 4 km/h (2 mph) or more below the set speed while the cruise control system
is operating.
4) The engine coolant temperature falls below 60°C (140°F) and vehicle speed is under 60 km/h (37
mph), or 35°C (95°F) and vehicle speed is under 40 km/h (25 mph).
The purpose of 1) and 2) above is to prevent the engine from stalling if the rear wheels lock up.
The purpose of 3) is to cause the torque converter clutch to operate to obtain torque multiplication. The
purpose of 4) is both to improve general driveability, and to speed up transmission warm±up.
Also, while the lock±up system is in operation, the ECM will temporarily turn it off during up±shift or down±
shift in order to decrease shifting shock. AT1±8
± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONOPERATION