coolant temperature TOYOTA SUPRA 1995 Service Repair Manual

SENSOR CHECK TROUBLE CODE CHART
If a LED is blinking during the diagnostic sensor check, check the circuit listed for the code in the table below
(Proceed to the page given for that circuit.)
 
 No.
 
 Blinking LED
 
 Detecting Condition
 0 L±AUTO 
Normal
 1 L±FACE*1 
Open or short in room temperature sensor circuit.
 2 L±B/L 
Open or short in ambient temperature sensor circuit.
 3 L±FOOT 
Open or short in evaporator temperature sensor circuit.
 4 L±F/D*2 
Open or short in engine coolant temperature sensor circuit.
 
5
 
L DEF*3 
Open in solar sensor circuit.
 5 L±DEF*3 
Short in solar sensor circuit.
 
 
 
6
 
 
 
L±A/C*4
 
 
 

All conditions below are detected for 3 secs. or more.
(a) Engine speed 450 rpm or more.
(b) Ratio between engine and compressor rpm deviates 20% or more in comparison to normal operation.
 
 

7
 
 

L±FRS
 
 


Open in pressure sensor circuit.

Abnormal refrigerant pressure [ below 196 kPa (2.0 kgf/cm2, 28 psi)
over 3,140 kPa (32.0 kgf/cm2, 455 psi) ] 
 8
 
 L±REC
 
 
Short to ground or power source circuit in air mix damper position sensor circuit.
 9 L±LO 
Short to ground or power source circuit in air outlet damper position sensor circuit.
 10 L±M2 
Air mix damper position sensor value does not change even if A/C amplifier signals the
air mix damper control servo motor to operate.
 
 11
 
 L±HI
 
 
Air outlet damper position sensor value does not change even if A/C amplifier signals the
air outlet damper control servo motor to operate.
HINT: *1If the room temp. is approx. ±20°C (±4°F) or lower, FACE light may blink even though the
system is normal.
*
2If the ambient temperature is approx. ±50°C (±58°F) or lower, the B/L light may blink even
though the system is normal.
*
3If the check is being performed in a dark place, the LED for DEF (solar sensor circuit abnormal)
could be blinking.
In this case, perform diagnostic sensor check again while shining a light, such as an inspection
light, on the solar sensor.
If the light is still blinking, there could be trouble in the solar sensor circuit. AC±20
± AIR CONDITIONING SYSTEMTROUBLESHOOTING

MATRIX CHART OF PROBLEM SYMPTOMS
If a normal code is displayed during the diagnostic sensor check but the trouble still occurs, perform trouble-
shooting for each problem symptom, checking the circuits for each symptom in the order given in the table
below (Proceed to the page given for each circuit).
AC±28
AC±30
AC±32
AC±34
AC±36
AC±38
AC±40
AC±42
AC±44
AC±46
AC±48
AC±50See page
Suspect Area
Symptom
Whole functions of the A/C system does not operate.
No blower operation
No blower control
Insufficient air flow
No cool air comes out
No warm air comes out
Output air is warmer or colder than the set
temperature or response is slow
No temperature control
(only Max. cool or Max. warm)
No air inlet control
No air outlet control
Engine idle up does not occur, or is continuous
Blinking of A/C indicator
Trouble code not recorded.
Set mode is cleared when IG switch is turned off.
Temperature Control
Air Flow Control
Room temp. sensor circuitAmbient temp. sensor
circuitEvaporator temp. sensorcircuitSolar sensor circuitEngine coolant temp. sensor
circuitPressure switch circuitAir mix damper positionsensor circuitAir mix damper controlservo motor circuitAir inlet damper controlservo motor circuitAir outlet damper controlservo motor circuitCompressor lock sensorcircuitAir outlet damper positionsensor circuit
AC±26± AIR CONDITIONING SYSTEMTROUBLESHOOTING

Blinking Light F D Engine Coolant Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the coolant temperature and sends the appropriate signals to the A/C amplifier.
These signals are used for warm up control when the engine is cold.
Diagnostic Sensor Check Detecting ConditionTrouble Area
Open or short in engine coolant temperature sensor
circuit.
Engine coolant temperature sensor

Harness or connector between engine coolant
temperature sensor and A/C amplifier

A/C amplifier
AC±34± AIR CONDITIONING SYSTEMTROUBLESHOOTING

INSPECTION PROCEDURE
(See page AC±26).
(See page IN±30)
Check voltage between terminals TW and SG of A/C amplifier connector.
Proceed to next circuit inspection shown on matrix
chart (See page AC±26). However, if the light is still
blinking, check and replace A/C amplifier.
Check engine coolant temperature sensor.
Replace engine coolant temperature sensor.
Check harness and connector between A/C amplifier and engine coolant
temperature sensor (See page
IN±30).
Repair or replace harness or connector.
Check and replace A/C amplifier.
Remove A/C amplifier with connectors still con-
nected.
1. Turn ignition switch ON.
2. Measure voltage between terminal TW of SG
of A/C amplifier connector at each temperature.
HINT: As the temperature increases, the voltage decreases
gradually.
Voltage:
at 0°C (32°F): 2.8 ~ 3.2 V
at 40°C (104°F): 1.8 ~ 2.2 V
at 70°C (158°F): 1.3 ~ 1.5 V
1. Remove A/C unit (See page AC±80).
2. Remove engine coolant temperature sensor.
Measure resistance between terminals 1 and 2 of en-
gine coolant temperature sensor connector at each
temperature.

HINT: As the temperature increases, the resistance
decreases gradually.
Resistance:
at 0°C (32°F): Below 50 k

at 40°C (104°F): 2.4 ~ 2.8 k

at 100°C (212°F): Over 0.2 k

± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±35

5. REMOVE AIR MIX SERVOMOTO
(a) Remove the defroster duct.
(b) Remove the 3 screws and the water valve cover.
(c) Disconnect the connector.
(d) Disconnect the control link.
(e) Remove the 2 screws and the air mix servomotor.
6. REMOVE HEATER RADIATOR AND WATER VALVE
(a) Remove the 2 screws and the plate.
(b) Remove the 2 screws and the clamp.
(c) Remove the 3 screws.
(d) Pull out the heater radiator with the water valve.
(e) Remove the 2 screws and water valve from the heater
radiator.
7. REMOVE HEATER AIR DUCT
Remove the 2 screws and the defroster air duct.
8. REMOVE VENT AIR DUCT
(a) Disconnect the control link.
(b) Remove the 2 screws and the vent air duct.
9. REMOVE ENGINE COOLANT TEMPERATURE SENSOR
(a) Disconnect the connector.
(b) After pulling off the clamp, pull out the sensor.
10. REMOVE AIR OUTLET SERVOMOTOR
(a) Disconnect the connector.
(b) Remove the 3 screws and the air outlet servomotor. AC±84
± AIR CONDITIONING SYSTEMAIR CONDITIONING UNIT

ENGINE COOLANT TEMPERATURE
SENSOR REMOVAL
1. REMOVE AIR CONDITIONING UNIT
(See page AC±80)
2. REMOVE ENGINE COOLANT TEMPERATURE SENSOR
(a) Disconnect the connector.
(b) After pulling off the clamp, pull out the sensor.
ENGINE COOLANT TEMPERATURE
SENSOR INSPECTION
(See page AC±34)
ENGINE COOLANT TEMPERATURE
SENSOR INSTALLATION
Installation is in the reverse order of removal. AC±106
± AIR CONDITIONING SYSTEMSENSOR

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

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

TROUBLESHOOTING
The table below will be useful for you in troubleshooting these electrical problems. The most likely causes
of the malfunction are shown in the order of their probability. Inspect each part in the order shown, and
replace the part when it is found to be faulty.
METER, GAUGES AND ILLUMINATION
 Trouble Parts name (See page)
 
 
 
Tachometer, Fuel Gauge and Engine Coolant Tempera-
ture Gauge do not operate
 
 
 
1. GAUGE Fuse (BE±6)
2. Meter Circuit Plate (BE±44)
3. Wire Harness
 
 
 
Speedometer does not operate
 
 
 
1. Vehicle Speed Sensor (BE±46)
2. Meter Circuit Plate (BE±44)
3. Wire Harness
 
 
 
 
Tachometer does not operate
 
 
 
 
1. Igniter
2. ECM (EG Section)
3. Meter Circuit Plate (BE±44)
4. Wire Harness
 
 
 
 
Fuel Gauge does not operate or abnormal operation
 
 
 
 
1. Fuel Receiver Gauge (BE±48)
2. Fuel Sender Gauge (BE±49)
3. Meter Circuit Plate (BE±44)
4. Wire Harness
 
 
 
 
Engine Coolant Temperature Gauge does not operate or
abnormal operation
 
 
 
 
1. Engine Coolant Temperature Receiver Gauge (BE±50)
2. Engine Coolant Temperature Sender Gauge (BE±50)
3. Meter Circuit Plate (BE±44)
4. Wire Harness
 
 
 
 
All illumination lights do not light up
 
 
 
 
1. TAIL Fuse (BE±6)
2. Light Control Rheostat (BE±54)
3. Meter Circuit Plate (BE±44)
4. Wire Harness
 
 
Only one illumination light does not light up 
 
1. Bulb
2. Meter Circuit Plate (BE±44)
± BODY ELECTRICAL SYSTEMCOMBINATION METERBE±41