1991 LEXUS SC400 clutch

(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 care as it could also
be due to loss of balance in the propeller shaft, differential,
torque converter clutch, etc..
(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 indi-
cated on the automatic shift schedule. (See page AT±45)
(e) Check 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±upON) of about 58 km/h (36 mph).
(2) Lightly depress the accelerator pedal and check that the engine RPM does not change abruptly.
If there is a big jump in engine RPM, there is no lock±up.
2. 2 POSITION TEST Shift into the 2 position and fully depress the accelerator ped-
al and check the following points:
(a) Check up±shift operation Check to see that the 1 "2 up±shift takes place and that the
shift point conforms to that shown on the automatic shift
schedule. (See page AT±45)
HINT:
w There is no O/D up±shift and lock±up in the 2 position.
(b) Check engine braking While running in the 2 position and 2nd gear, release the ac-
celerator pedal and check the engine braking effect.
AT±42
±
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EVALUATION
 

Problem\
 
\

\
Possible cause 


\
 
\

\

Engine output may be insufficient.
 \
 \
 Stator one±way clutch is operating properly
 (a) Stall speed low in D and R positions.\
 \
HINT:
 \
 \
If more than 600 RPM below the specified value, the
 \
 \
torque converter could be faulty.
 \
 \
 Line pressure too low
 
(b) Stall speed high in Dposition
\
 \
 Forward clutch slopping 

(b) Stall speed high in D position.\
 
\
 No.2 one±way clutch not operating properly 


\
 
\

\

O/D one±way clutch not operating properly
 \
 \
 Line pressure too low
 (c) Stall speed high in Rposition\
 \
 Direct clutch slipping
 (c) Stall speed high in R position.\
 \
 First and reverse brake slipping
 \
 \
 O/D one±way clutch not operating properly
 \
 \
 Line pressure too low
 (d) Stall speed high in D and R position.\
 \
 Improper fluid level 

\
 
\
 O/D one±way clutch not operating properly
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±51
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TIME LAG TEST
When the shift lever is shifted while the engine is idling, there will be a \
certain time lapse or lag before the
shock can be felt. This is used for checking the condition of the O/D direct \
clutch, forward clutch, direct
clutch, and first and reverse brake.
NOTICE:
Perform the test at normal operating fluid temperature 50±80 C (122±176 F).
 Be sure to allow a one minute interval between tests.
 Make 3 measurements and take the average value.
MEASURE TIME LAG
(a) Fully apply the parking brake
(b) Start the engine and check idle speed.
Idle speed:
650 RPM (In N position and air conditioner OFF)
(c) Shift the shift lever from N to D position. Using a stop watch, measure the time it take\
s from shifting thelever until the shock is felt.
In same manner, measure the time lag for N
R.
Time lag:
N D Less than 1.2 seconds
N R Less than 1.5 seconds
AT±52±
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EVALUATION
If N " D or N " R time lag are longer than specified:
 Problem\
 \
Possible cause 






N " D time lag is longer
\
 
\


\


\

\


Line pressure too low
 Forward clutch worn
 O/D one±way clutch not operating properly
 Accumulator back pressure too low
 






N " R time lag is longer
\
 
\


\


\

\


Line pressure too low
 Direct clutch worn
 First and reverse brake worn
 O/D one±way clutch not operating properly
 Accumulator back pressure too low
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±53
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SPECIFIED LINE PRESSURE
 
Condition
 
D positionkPa (kgf/cm2, psi)
 
R positionkPa (kgf/cm2, psi) 

Idling
 

382±441 (3.9±4.5, 55±64)
 

637±716 (6.5±7.3, 92±104) 

Stall
 

1,265±1,402 (12.9±14.3, 183±203)
 

1,726±2,060 (17.6±21.0, 250±299)
If the measured pressures are not up to specified values, recheck the thro\
ttle cable adjustment and perform
a retest.
EVALUATION
 Problem\
 \
Possible cause
 \
 \

Throttle cable out of adjustment If the measured values at all positions are higher.\
 \
 Throttle valve defective 


\

\

\

Regulator valve defective
 \
 \
 Throttle cable out of adjustment
 \
 \
 Throttle valve defective
 If the measured values at all positions are lower.\
 \
 Regulator valve defective
 \
 \
 Oil pump defective
 \
 \
 O/D direct clutch defective
 
Ifpressure is low in the Dposition only
\
 \
 D position circuit fluid leakage If pressure is low in the D position only.\
 \
 Forward clutch defective 


\

\

\

R position circuit fluid leakage
 If pressure is low in the R position only.\
 \
 Direct clutch defective
 \
 \
 First and reverse brake defective
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±55
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\
 

\


\

\

Trouble Area
 




O/D OFF
Light*1
Blinks
 




Memory*2
 




See
Page
\
 \
   
\
 \

Harness or connector between No. 1 vehicle speed sensor and ECM.   
\
 \

No. 1 vehicle speed sensor. 

 

 
AT±78\
 \

Combination meter.   AT±78
\
 \

ECM   
\
 \
   
\
 
\
\
 
\

\


Harness or connector between No.4 solenoid and ECM.
\
 \

No.4 solenoid.XAT±82
\
 \

ECM
\
 \

\
 \
   
\
 \

Harness or connector between No.2 vehicle speed sensor and ECM.   
\
 \

No.2 vehicle speed sensor.   AT±86\
 
\

ECM 

 

 
\
 
\

\

 


 


 


\
 \

\
 \


Harness or connector between No.1 solenoid and ECM.
\
 \

No.1 solenoid.AT±90
\
 \

ECM
\
 \

\
 \

\
 
\

Harness or connector between No.2 solenoid and ECM.\
 
\

\


No.2 solenoid.AT±90
\
 \

ECM
\
 \

\
 \

\
 \

Harness or connector between No.3 solenoid valve and ECM.
\
 \

No.3 solenoid valve.XAT±94\
 \

ECM\
 
\
\
 
\

\

\
 \


Harness or connector between O/D direct clutch speed sensor and ECM.
\
 \

O/D direct clutch speed sensor.AT±98
\
 \

ECM
\
 \

±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±61
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DTC46No. 4 Solenoid Valve Circuit (For Accumula-
tor Back Pressure Modulation)
CIRCUIT DESCRIPTION
The No. 4 solenoid valve controls the hydraulic pressure acting on the
brakes and clutches of the planetary gear units when gears are shifted and
performs smooth gear shifting.
The ECM determines optimum operating pressure according to the signals
from the throttle position sensor, vehicle speed sensor and O/D clutch
speed sensor and controls the volume of current flow to the solenoid valve.
The amount of electric current to the solenoid is controlled by the (*) \
duty
ratio of ECM out put signals, causing momentary change to the hydraulic
pressure acting on the clutches during gear shifting.
When the duty ratio is high, the hydraulic pressure acting on the clutch\
es
is low.
(*) Duty Ratio
The duty ration is the ration of the period of continuity in one cycle. For\
example, if A is the period of continuity
in one cycle, and B is the period of non±continuity, then
DTC No.DTC Detecting ConditionTrouble Area
46
All conditions below are detected for 1 sec. or more.
2trip detection logic*
(a) ECM outputs duty signal to No. 4 solenoid in 90%
or higher duty ratio.
(b) Current to No. 4 solenoid:330
100 Ma OR LESS
(O/D OFF indicator light doesn't blink)
 No. 4 solenoid valve.
 Harness or connector between No. 4 sole-
noid valve and ECM
 ECM
*: See page AT±62.
Reference Reference
 Waveform between terminals SLN± and E
1when engine is idling. 
Waveform between terminals SLN± and E1 during shift
change.
AT±82±
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This sensor detects the rotation speed of the O/D input shaft from the
rotation of the O/D direct clutch drum.
Its construction is the same as that of the No. 2 vehicle speed sensor
(See page AT±86).
By comparing the O/D direct clutch speed signal and the No. 2 vehicle
speed sensor signal, ECM detects the shift timing of the gears and ap-
propriately controls the engine torque and hydraulic pressure in re-
sponse to various conditions, thus performing smooth gear shift.
DTC67O/D Direct Clutch Speed Sensor Circuit
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
67
All conditions below are detected for 4 secs. or more
2 trip detection logic*
(a) Gear position: 1st, 2nd and 3rd
(b) T/M input shaft rpm: 100 rmp or more
(c) T/M output shaft rpm: less than 300 rpm
(d) PNP: OFF (other than P or N position)

O/D direct clutch speed sensor.

Harness or connector between O/D direct
clutch speed sensor and ECM.

ECM
*: See page AT±62.
Reference

Wave form between terminals NCO
+ and NCO± during engine idling.
AT±98
±
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