1991 LEXUS SC400 Throttle Position

CHECK TERMINAL TT OUTPUT
VOLTAGE
AT00R±01
When a voltmeter is connected to the DLC1, the following
items can be checked.
1. Throttle position sensor signal
2. Brake signal
3. Shift position signal
1. VOLTMETER CONNECTION Connect the positive (+) probe of the voltmeter to terminal T
T
and the negative (±) probe to terminal E1 of the DLC2.
HINT: If a voltmeter with small internal resistance is used, the
correct voltage will not be indicated, so use a voltmeter with
an internal resistance of at least 10 k
.
2. TURN IGNITION SWITCH TO ON (DO NOT START THE
ENGINE)
3. CHECK THROTTLE POSITION SENSOR SIGNAL Check if the voltage changes from approximately 0 V to
approximately 8 V when the accelerator pedal is gradually
depressed from the fully closed position.
4. CHECK BRAKE SIGNAL (LOCK±UP CUT SIGNAL)
(a) Open the throttle valve fully to apply approximately 8 V to terminal T
T.
(b) In this condition, check terminal T
T voltage when the brake
pedal is depressed and released.
TT terminal voltage:
0 V (When brake pedal is depressed)
8 V (When brake pedal is released)
5. START ENGINE
6. CHECK SHIFT POSITION SIGNAL (VEHICLE SPEED ABOVE 60 KM/H OR 37 MPH)
Check up±shifting together with terminal T
T voltage.
HINT: Check for light shocks from up±shifting and for
changes in the tachometer.
 Gear Position Terminal TT output voltage 1st GearBelow 0.5 V 

2nd Gear1.5 ~
2 6 V
 3rd Gear3.5 ~ 4.6 V
 3rd Lock±up4.5 ~ 5.9 V
 O/D5.5 ~ 6.9 V
 O/D Lock±up6.5 ~ 7.9 V
If terminal TT output voltage check cannot be performed, per-
form the check of terminal T
T circuit on page AT±120.
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AT09W±09
AUTOMATIC SHIFT SCHEDULE
SHIFT POINT
NORM Mode (Kick±down foot switch activated)
 Shift position Shifting point Vehicle speed km/h (mph)
  Throttle valve fully opened 1"2 67±71 (42±44)
  2"3 118±124 (73±77)
 Dposition 3"O/D 170±177 (106±110)
 
D position
 O/D"3 164±170 (102±106)
  3"2 105±111 (65±69)
  2"1 53±57 (33±35)
  Throttle valve fully opened 1"2 67±71 (42±44)
 2 position 3"2 106±112 (66±70)
  2"1 53±57 (33±35)
 Lposition Throttle valve fully opened 3"2 104±109 (65±68)
 
L position
 2"1 57±63 (35±39)
NORM Mode (Kick±down foot switch deactivated)
 Shift position Shifting point Vehicle speed km/h (mph)  Throttle valve fully opened 1"2 67±71 (42±44)  2"3 118±124 (73±77)  3"O/D 155±161 (96±100) 
Dposition
 O/D"3 128±134 (79±83) D position 3"2 71±75 (44±47)  2"1 10±13 (6±8)  Throttle valve fully closed 3"O/D 32±35 (20±22)  O/D"3 23±26 (14±16)  Throttle valve fully opened 1"2 67±71 (42±44) 2 position 3"2 106±112 (66±70)  2"1 10±13 (6±8) 
Lposition
 Throttle valve fully opened 3"2 104±109 (65±68) L position 2"1 57±63 (35±39)
PWR Mode (Kick±down foot switch activated)
 Shift position Shifting point Vehicle speed km/h (mph)  Throttle valve fully opened 1"2 67±71 (42±44)
  2"3 116±124 (73±77)
 
Dposition
 3"O/D 179±186 (111±116)
 D position O/D"3 164±170 (102±106)
  3"2 105±111 (65±69)
  2"1 53±57 (33±35)
  Throttle valve fully opened 1"2 67±71 (42±44)
 2 position 3"2 106±112 (66±70)
  2"1 53±57 (33±35)
 
Lposition
 Throttle valve fully opened 3"2 104±109 (65±68)
 L position 2"1 57±63 (35±39)
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PWR Mode (Kick±down foot switch deactivated)
Shift positionShifting pointVehicle speed km/h (mph)  Throttle valve fully opened 1"2 67±71 (42±44)  2"3 118±124 (73±77)  3"O/D 179±186 (111±116) 
Dposition
 O/D"3 149±155 (93±96) D position 3"2 95±100 (59±62)  2"1 22±26 (14±16)  Throttle valve fully closed 3"O/D 32±35 (20±22)  O/D"3 23±26 (14±16)  Throttle valve fully opened 1"2 67±71 (42±44) 
2 position
 3"2 106±112 (66±70)  2"1 10±13 (6±8) 
Lposition
 Throttle valve fully opened 3"2 104±109 (65±68) L position 2"1 57±63 (35±39)
LOCK±UP POINT
NORM Mode
 D position km/h (mph) 
Lock±upON
 
Lock±upOFF Throttle valve opening 5% Lock±up ON Lock±up OFF
 *3rd Gear 83±88 (52±55) 77±82 (48±51)
 O/D Gear 56±60 (35±37) 53±57 (33±35)
*: O/D Switch OFF
PWR Mode
D position km/h (mph)Lock±upONLock±upOFF Throttle valve opening 5%Lock±up ONLock±up OFF
 *3rd Gear 83±88 (52±55) 77±82 (48±51)
 O/D Gear 56±60 (35±37) 53±57 (33±35)
*: O/D Switch OFF
HINT:
(1) There is no lock±up in the 2 and L positions.
(2) In the following cases, the lock±up will be released regardless\
of the lock±up pattern.

When the throttle valve is completely closed.

When the brake light switch is ON.
(3) Shift up to 3rd will not occur when the engine coolant temp. is below 3\
5 C (95 F) and the vehicle speed
is below 40 km/h (25 mph).
(4) Shift±up to O/D will not occur when the engine coolant temp. is\
below 60 C (140 F) and the vehicle
speed is below 63 km/h (39 mph).
(5) During cruise control operation, the shift pattern is fixed in NOR\
M. And when the vehicle speed drops to 10 km/h (6 mph) or more below the cruise control set vehicle speed, s\
hift down from O/D to 3rd
occurs.
(6) The kick±down foot switch turns ON when the accelerator pedal i\
s depressed further with the throttle valve already fully open.
AT±46
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(f) Check the fluid level at the normal operating temperature70±80
C (158±176
F) and add as necessary.
NOTICE: Do not overfill.
4. CHECK FLUID LEAKS
Check for leaks in the transmission.
If there are leaks, it is necessary to repair or replace O±rings,
seal packings, oil seals, plugs or other parts.
5. INSPECT AND ADJUST THROTTLE CABLE
(a) Remove the 2 bolts, nut and throttle body cover.
(b) Check that the throttle valve is fully closed.
(c) Check that the inner cable is not slack.
(d) Measure the distance between the outer cable end and stopper on the cable.
Standard distance:
0±1 mm (0±0.04 in.)
If the distance is not standard, adjust the cable by the adjust-
ing nuts.
(e) Install the throttle body cover, and two bolts and nut.
6. INSPECT AND ADJUST SHIFT LEVER POSITION When shifting the shift lever from the N position to other posi-
tions, check that the lever can be shifted smoothly and accu-
rately to each position and that the position indicator correctly
indicates the position.
If the indicator is not aligned with the correct position, carry
out the following adjustment procedures:
(a) Loosen the nut on the control shaft lever.
(b) Push the control shaft lever fully rearward.
(c) Return the control shaft lever 2 notches to N position.
(d) Set the shift lever to N position.
(e) While holding the shift lever lightly toward the R position side,
tighten the shift lever nut.
(f) Start the engine and make sure that the vehicle moves forward when shifting the lever from the N to D position and
reverses when shifting it to the R position.
AT±48
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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
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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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DTC61No.2 Vehicle Speed Sensor Circuit
CIRCUIT DESCRIPTION
The No.2 speed sensor detects the rotation speed of the transmission output shaft and sends signals to the
ECM. The ECM determines the vehicle speed based on the these signals. An AC voltage i\
s generated in the
No.2 vehicle speed sensor coil as the rotor mounted on the output shaft rota\
tes, and this voltage is sent to the
ECM.
The gear shift point and lock±up timing are controlled by the ECM based \
on the signals from this vehicle speed
sensor and the throttle position sensor signal.
If the No.2 vehicle speed sensor malfunctions, the ECM uses input signals \
from the No.1 vehicle speed sensor
as a back±up signal.
DTC No.DTC Detecting ConditionTrouble Area
61
All conditions below are detected 500 times or more
continuously.
2 trip detection logic*
(a) No No.2 vehicle speed sensor signal in 4 No.1 ve-
hicle speed sensor signal pulses.
(b) Vehicle speed: 5.6 MPH (9 km/h) or more for
at least 4 secs.
(c) Park/neutral position switch:
OFF (Other than P or N position)

No. 2 vehicle speed sensor

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

ECM
*: See page AT±62
Reference

Waveform between terminals SP2+ and SP2± when vehicle speed is approx.\
37 MPH (60km/h).
AT±86
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WIRING DIAGRAM
AT±66
IN±33
Throttle Position Sensor Circuit
CIRCUIT DESCRIPTION
The throttle position sensor detects the throttle valve opening angle and s\
ends signals to ECM.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
AT±102±
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