1995 TOYOTA SUPRA cruise control

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

ARRANGEMENT OF COMPONENTS
 No. Components Function
 
1Pattern Select Switch Selects the Manual mode or the Normal mode for shift 1 Pattern Select Switch Selects the Manual mode or the Normal mode for shift
and lock±up timing. 
2Crankshaft Position SensorDetects the engine speed 2 Crankshaft Position Sensor Detects the engine speed.
 3Park/Neutral Position SwitchDetects the shift lever position

3 Park/Neutral Position Switch Detects the shift lever position.
 
4Stop Light SwitchDetects if the brake pedal is depressed 4 Stop Light Switch Detects if the brake pedal is depressed.
5Throttle Position SensorDetects the throttle valve opening angle 5 Throttle Position Sensor Detects the throttle valve opening angle.
 
6O/D Main Switch Prevents up±shift to the O/D gear if the O/D main 6 O/D Main Switch Prevents u shift to the O/D gear if the O/D main
switch is off.
 
 7Cruise Control ECU
This ECU prevents the transmission from shifting into
O/D and prohibits lock up control when the vehicle's 7 Cruise Control ECU O/D and prohibits lock±up control when the vehicle's
speed drops below the cruise control set speed parameter.
AT1±10± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONOPERATION

PROBLEM SYMPTOM CONFIRMATION
Taking into consideration the results of the customer problem analysis, try to reproduce the symptoms of
the trouble. If the problem is that the transmission does not up±shift, does not down±shift, or the shift point
is too high or too low, conduct the following road test to confirm the automatic shift schedule and simulate
the problem symptoms.
ROAD TEST
NOTICE: Do the test at normal A/T fluid operating temp.
50±80°C (122 ± 176°F).
1. D POSITION TEST (NORM PATTERN)
Shift into the D position and keep the accelerator pedal
constant at the full throttle valve opening position, and check
the following points:
(a) Check up±shift operation.
Check that 1±2, 2±3 and 3±O/D up±shift takes place, at the
shift point shown in the automatic shift schedule.
(See page AT1±96)
HINT:
(1) O/D Gear Up±shift Prohibition Control.
w Coolant temp. is 60°C (140°F) or less.
w If there is a 10 km/h (6 mph) difference between the set
cruise control speed and
wvehicle speed.
wO/D main switch is pushed ON.
w(During O/D OFF, indicator light lights up.)
(2) O/D Gear Lock±up Prohibition Control.
w Brake pedal is depressed.
w Coolant temp. is 60°C (140°F) or less.
(b) Check for shift shock and slip.
Check for shock and slip at the 1±2, 2±3 and 3±O/ D up±
shifts.
(c) Check for abnormal noise and vibration.
Run at the D position lock±up or O/D gear and check for ab-
normal noise and vibration.
HINT: The check for the cause of abnormal noise and vibra-
tion must be performed very thoroughly as it could also be
due to loss of balance in the torque converter clutch, etc.
± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONTROUBLESHOOTINGAT1±37

(d). Check kick±down operation.
While running in the D position, 2nd, 3rd and O/D gears,
check to see that the possible kick±down vehicle speed limits
for 2 " 1, 3 " 2 and O/D " 3 kick±downs conform to those
indicated on the automatic shift schedule. (See page
AT1±96)
(e) Check for abnormal shock and slip at kick±down.
(f) Check the lock±up mechanism.
(1) Drive in D position, O/D gear, at a steady speed (lock±up
ON) of about 61 km/h (38 mph).
(2) Lightly depress the accelerator pedal and check that the
RPM does not change abruptly.
If there is a big jump in RPM, there is no lock±up.
2. D POSITION TEST (MANU PATTERN)
Shift into the D position and hold the accelerator pedal
constant at the full throttle valve opening position, and check
the following points:
(a) Check up±shift operation.
2±3 and 3±O/D up shifts should take place, and shift points
should conform to those shown in the automatic shift sched-
ule.
(See page AT1±96)
HINT:
w O/D up±shift or lock±up will not occur when the engine
coolant temp. is below 605C (1405F) and speed is under
63 km/h (39 mph), or if there is a 10 km/h (6 mph)
difference between the set cruise control speed.
w 3rd up±shift or lock±up will not occur when engine
coolant temp. is 355C (955F) and speed is under 40 km/h
(25 mph).
(b) Check for shift shock and slip.
In the same manner, check the shock slip at the 2 " 3 and
3 " O/D up±shifts. AT1±38
± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONTROUBLESHOOTING

INSPECTION PROCEDURE
Shift the shift lever to N position.
Jack up one of the rear wheels.
Connect the Check Harness A
(See page EG±404)
Disconnect power steering ECU connector
and cruise control ECU connector.
Turn ignition switch ON.
Measure voltage between terminal SP1 of ECM
connector and body ground when the wheel is
turned slowly.
Check voltage between terminal SP1 of ECM connector and body ground.
Voltage is generated intermittently.
Check and replace ECM.
Repair or replace harness or connector be-
tween ECM and telltale light RH.
Check operation of odometer and trip meter (telltale light RH (See page
BR±48))
AT1±67± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONTROUBLESHOOTING

O D Cancel Signal Circuit
CIRCUIT DESCRIPTION
While driving with cruise control activated, in order to minimize gear shifting and provide smooth uphill cruising,
overdrive may be prohibited temporarily in some conditions.
The Cruise Control ECU sends O/D cut signals to the ECM as necessary and the ECM cancels overdrive shifting
until these signals are discontinued.
(For details, see the cruise control section, page BE±162)
WIRING DIAGRAM
INSPECTION PROCEDURE
Connect the Check Harness A to the ECM
(See page EG±404).
Turn ignition switch ON.
Check and replace ECM.
Check voltage between terminal OD1 of ECM connector and body ground.
Measure voltage between terminal OD1 of ECM
connector and body ground.
Proceed to next circuit inspection shown on
matrix chart (See page AT1±58).
Voltage: 4 ± 6 V
± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONTROUBLESHOOTINGAT1±91

Disconnect Cruise Control ECU connector.
Turn ignition switch ON.
Repair or replace harness or connector.
Check and replace ECM.
Check voltage between terminal OD of Cruise Control ECU harness side
connector and body ground.
Measure voltage between terminal OD of Cruise
Control ECU harness side connector and body
ground.
Voltage 4 ± 6 V
Check and replace Cruise Control ECU.
Check harness and connector between Cruise Control ECU and ECM (See
page IN±30).
AT1±92± AT340E (2JZ±GE) AUTOMATIC TRANSMISSIONTROUBLESHOOTING