TOYOTA SUPRA 1995 Service Repair Manual

INPUT SIGNAL CHECK
Output Code
1. (a) For check No.1 No.3
Turn the ignition switch on.
(b) For check No.4
Jack up the vehicle.
Start the engine.
2. Turn the control switch to SET/COAST position or RES/ACC
position and hold it down or up (1).
3. Push the main switch on (2).
4. Check that the CRUISE MAIN indicator light blinks twice or
3 times repeatedly.
5. Turn the SET/COAST switch or RES/ACC position off.
6. Operate each switch as listed in the table below.
7. Read the blinking pattern of the CRUISE MAIN indicator light.
8. After performing the check, turn the main switch off.
HINT: When two or more signals are input to the ECU, only
the lowest±numbered code is displayed.
Turn SET/COAST switch ON.
Turn RES/ACC switch ON.
Turn CANCEL switch ON.
Turn stop light switch ON.
(Depress brake pedal)
Turn parking brake switch ON.
(Pull up the parking brake lever).
Turn neutral start switch OFF.
(Shift to EXCEPT D RANGE).
Turn clutch switch OFF.
(Depress clutch pedal)
Drive at 40 km/h (25 mph) or
higher.
Drive at 40 km/h (25 mph) or
below.
SET/COAST switch circuit is
normal.
RES/ACC switch circuit is
normal.
CANCEL switch circuit is
normal.
Stop light switch circuit is
normal.
Parking brake switch circuit
is normal.
Neutral start switch circuit is
normal.
Clutch switch circuit is
normal.
Speed sensor is normal.
DiagnosisOperation MethodCRUISE MAIN Indicator Light
Blinking Pattern
± BODY ELECTRICAL SYSTEMBE±169CRUISE CONTROL SYSTEM

IN±35BE±171BE±197BE±179BE±182BE±191BE±189BE±177BE±184BE±165IN±30
See page
Inspection Item
Problem
ªCRUISEº Indicator light blinks.
Cruise control system does not set.
Cruse control system does not
operate.
Diagnosis Trouble Code
Indicator light does not light up
Large speed drop when the cruise control switch
turned to SET.
Vehicle speed fluctuates when cruise control
switch turned to SET.
Set speed deviates on high or low side.
Acceleration response is sluggish when cruise
control switch turned to ªACCELº or ªRESUMEº
Cruise control system does not set.
Cruise control system does not operate.
Set speed does not cancel when brake pedal
depressed.
Set speed does not cancel when parking brake
lever pulled.
Cruise control not cancelled, even when
transmission is shifted to EXCEPT D RANGE.
Set speed does not cancel when clutch pedal
depressed.
Set speed does not cancel when cruise control
switch turned to CANCEL.
Vehicles speed does not decrease when cruise
control switch turned to COAST.
Vehicle speed does not accelerate when cruise
control switch turned to ACCEL.
Vehicle speed does not return to memorized
cruise when control switch turned to RESUME.
Speed can be set below about 40 km/h
(25 mph.)
Cruise control does not disengage even at about
40 km/h (25 mph) or less.
Indicator LightCruise Control ECUActuatorMain Switch
(in Control Switch)Control SwitchStop Light SwitchClutch Switch or Park/
Neutral Position SwitchParking Brake SwitchVehicle Speed SensorSpeed Control Cable
FunctionThrottle Position Sensor
(IDL)Wire Harness
Source voltage drop
MATRIX CHART OF PROBLEM SYMPTOMS
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. BE±170
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

CIRCUIT INSPECTION
DTC 11 14 41 Actuator Motor Circuit
CIRCUIT DESCRIPTION
The actuator motor is operated by signals from the ECU. Acceleration and deceleration signals are
transmitted by changes in the Duty Ratio (See note below).
Duty Ratio
The duty ratio is the ratio of the period of continuity in one cycle. For example, if A is the period of conti-
nuity in one cycle, and B is the period of non±continuity, then
Overcurrent (short) in motor circuit.
Open in actuator motor circuit.
Duty ratio of 100 % output to motor
acceleration side.
Cruise control actuator motor
Harness or connector between actuator
motor and ECU
ECU
CodeDiagnosisTrouble area
11
14
41
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±171

(1)Remove cruise control actuator.
(2)Disconnect actuator connector.
(1)Connect positive (+) lead to terminal 5 and
negative (±) lead to terminal 4 of actuator connector.
(Magnet clutch ON)
(2)When battery positive voltage is applied to each of
the actuator connector terminals check that the con-
trol plate moves smoothly without hesitating.
(3) With the motor rotating as in 2., check that the mo±
tor is stopped by limit switches when the control
plate moves to fully opened or fully closed position.
Replace actuator assembly.
Repair or replace harness or connector.
Check harness and connectors between cruise control ECU and actuator
motor (See page IN±30).
 
 Proceed to next circuit inspection shown on matrix chart (See page BE±170).
However, when diag. trouble code 11, 14, 41 is displayed, check and replace cruise control ECU.
BE±172± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

DTC 12 Actuator Magnet Clutch Circuit
CIRCUIT DESCRIPTION
This circuit turns on the magnet clutch inside the actuator during cruise control operation according to the signal
from the ECU. If a malfunction occurs in the actuator or speed sensor, etc. during cruise control, the rotor shaft
between the motor and control plate is released.
When the brake pedal is depressed, the stoplight switch turns on, supplying electrical power to the stoplight.
Power supply to the magnet clutch is mechanically cut and the magnet clutch is turned OFF.
When driving downhill, if the vehicle speed exceeds the set speed by 15 km/h (9 mph), the ECU turns the magnet
clutch OFF. If the vehicle speed later drops to within 10 km/h (6 mph) above the set speed, then cruise control
at the set speed is resumed.
 Code No. Diagnosis Trouble area
 
 
 
 
 
12
 
 
 
 
 
Overcurrent (short) in magnet clutch
circuit.
Open (0.8 sec) in magnet clutch circuit.
 
 
 
 
 
Cruise control magnet clutch.
Harness or connector between ECU and
magnet clutch, magnet clutch and body
ground.
ECU
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±173

(See page IN±30)
(1) Connect positive  lead to terminal 5 and negative
lead to terminal 4 of actuator connector.
(2) Move the control plate by hand.
Replace stop light switch.
Repair or replace harness or connector.
Check for open and short in harness and connectors between ECU and stop light switch,
stop light switch and magnet clutch, magnet clutch and body ground. (See page
IN±30).
(1) Remove cruise control actuator.
(2) Disconnect actuator connector.
Move the control plate by hand.
Control plate moves. (Magnet clutch off)
Control plate doesn't move. (Magnet clutch on)
Replace actuator assembly.
Disconnect stop light switch connector.
Check continuity between terminals.
Continuity
Terminals
Switch pin free
Switch position
(Brake pedal depressed)
Switch pin pushes in
(Brake pedal released)
Check actuator magnet clutch.
Check stop light switch.
INSPECTION PROCEDURE
 
 
Proceed to next circuit inspection shown on matrix chart (See page BE±170).
However, when diag. trouble code 12, is displayed, check harness and connector for loose
connection. If connection is normal, check and replace ECU.
BE±174± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

DTC 13 14 Actuator Position Sensor Circuit
CIRCUIT DESCRIPTION
This circuit detects the rotation position of the actuator control plate and sends a signal to the ECU.
 
 Code No.
 
 Diagnosis
 
 Trouble area
 13   Position sensor detects abnormal voltage.   Cruise control actuator position sensor.
 
13
 
Position sensor detects abnormal voltage.
 
Cruise control actuator osition sensor.

 Harness or connector between actuator
14Position sensor signal value does notposition sensor and body ground. 14   Position sensor signal value does not
hhtht t osition sensor and body ground.
ECU 
14
 change when the motor operates.   ECU
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±175

Repair or replace harness or connector.
Check for open and short in harness and connector between ECU and actuator
position sensor (See page
IN±30).
(1) Turn ignition switch ON.
(2) Measure voltage between terminals VR2 and
VR3 of ECU connector while turning control plate
slowly by hand from the deceleration side to the
acceleration side.
Voltage:
Check actuator position sensor.
Replace actuator assembly.Replace actuator assembly.
Check voltage between terminals VR2 and VR3 of ECU connector.
Fully closed: approx. 1.3 V
Fully opened: approx. 4.1 V
In addition, as the control plate is turned, the volt-
age should increase gradually without interruption.
Remove ECU with connectors still connected.
Proceed to next circuit inspection shown on
matrix chart (See page BE±170).
Resistance:
Fully closed: Approx. 260 k

In addition, as the control plate turns, the resistance
should increase gradually without interruption.
Fully opened: Approx. 2.2 k

Measure resistance between actuator terminals 1 and
3 of actuator connector.
Resistance: Approx. 2.2 k

Measure resistance between actuator terminals 2 and
3 of actuator connector, while turning the control plate
slowly by hand from the deceleration side to the ac-
celeration side.
(1) Remove cruise control actuator.
(2) Disconnect the actuator connector.
INSPECTION PROCEDURE
 
 Check harness and connector for loose connection.
If connection is normal check and replace ECU.
BE±176± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

DTC 21 23 Speed Sensor Circuit
The speed sensor signal is sent to cruise control ECU as ve-
hicle speed signal.
The rotor shaft is driven by the gear of the transmission. For
each rotation of the shaft, the speed sensor sends a 4±pulse
signal to the combination meter.
This signal is converted inside the combination meter and
sent as a 4±pulse signal to the cruise control ECU.
The ECU calculates the vehicle speed from this pulse fre-
quency.
CIRCUIT DESCRIPTION
Speed signal is not input to the ECU while
cruise control is set..
Vehicle speed decrease 16 km/h or more
than preset speed.
Vehicle speed sensor pulse is abnormal.
Speed sensor
Combination meter
Harness or connector between speed sen-
sor and combination meter, combination
meter and ECU.
ECU
Actuator
Speed sensor
Harness or connector in OD and SPD cir-
cuit (Open or short intermittently)
ECU
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±177

WIRING DIAGRAM
INSPECTION PROCEDURE
page BE±41).
Repair or replace speed sensor, harness,
connector or combination meter assembly.
Proceed to next circuit inspection shown on
matrix chart (See page BE±170).
(1) See input signal check on page BE±169.
(2) Check indicator light operation when driving with
vehicle speed above 40 km/h (25 mph), and with
vehicle speed below 40 km/h (25 mph).
Input signal check.
Check speedometer circuit (See combination meter troubleshooting on
Vehicle speed above 40 km/h (25 mph):
Indicator light blinks
Vehicle speed below 40 km/h (25 mph):
Indicator light stays on
Check harness and connector for loose connection.
If connection is normal, check and replace ECU. BE±178
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM