1991 LEXUS SC400 Brake Pedal

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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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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AT00S±01
PRELIMINARY CHECK
1. CHECK FLUID LEVELHINT:
wDrive the vehicle so that the engine and transmission
are at normal operating temperature.
Fluid temp.: 70±80 5C (158±176 5F)
w Only use the COOL range on the dipstick as a rough
reference when the fluid is replaced or the engine does
not run.
(a) Park the vehicle on a level surface and set the parking brake.
(b) With the engine idling and the brake pedal depressed, shift the shift lever into all positions from P to L position and return
to P position.
(c) Pull out the transmission dipstick and wipe it clean.
(d) Push it back fully into the tube.
(e) Pull it out and check that the fluid level is in the HOT range. If the level is at the low side, add fluid.
Fluid type:
ATF TYPE T±II or Equivalent
NOTICE: Do not overfill.
2. CHECK FLUID CONDITION If the fluid smells burnt or is black, replace it.
3. REPLACE TRANSMISSION FLUID
(a) Remove the drain plug and drain the fluid.
(b) Reinstall the drain plug securely.
(c) With the engine OFF, add new fluid through the oil filler tube.
Fluid type:
ATF TYPE T±II or Equivalent
Capacity:
Total: 8.2 liters (8.7 US qts, 7.2 lmp. qts)
Drain and refill: 1.9 liters (2.0 US qts, 1.7 lmp. qts)
(d) Start the engine and shift the shift lever into all positions fromP to L position and then shift into P position.
(e) With the engine idling, check the fluid level. Add fluid up to the
COOL level on the dipstick.
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A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±47
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MECHANICAL SYSTEM TESTS
AT0QT±01
STALL TESTThe object of this test is to check the overall performance of the trans\
mission and engine by measuring
the stall speeds in the D and R positions.
NOTICE:
 Perform the test at normal operating fluid temperature 50±80 C (122±176 F).
 Do not continuously run this test longer than 5 seconds.
 To ensure safety, conduct this test in a wide, clear, level area, which provides good traction.
 The stall test should always be carried out in pairs. One technician sho\
uld observe the conditions of
wheels or wheel stoppers outside the vehicle while the other is performi\
ng the test.
MEASURE STALL SPEED
(a) Chock the 4 wheels.
(b) Connect a tachometer to the engine.
(c) Fully apply the parking brake.
(d) Keep your left foot pressed firmly on the brake pedal.
(e) Start the engine.
(f) Shift into the D position. Step all the way down on the accelerator peda\
l with your right foot.
Quickly read the stall speed at this time.
Stall speed:
2,200 + 150 RPM
(g) Perform the same test in R position.
AT±50±
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MEASURE LINE PRESSURE
NOTICE:
Perform the test at normal operating fluid temperature 50±80 C (122±176 F).
 The line pressure test should always be carried out in pairs. One technicia\
n should observe the
conditions of wheels or wheel stoppers outside the vehicle while the other is perf\
orming the test.
 Be careful to prevent the oil pressure gauge hose from interfering with \
the exhaust pipe.
(a) Warm up the transmission fluid.
(b) Remove the test plug on the transmission case left side and connect the \
oil pressure gauge SST.
SST 09992±00094
HINT: Connecting the oil pressure gauge will be made easier by moving LH sid\
e heat insulator aside.
(c) Fully apply the parking brake and chock the 4 wheels.
(d) Start the engine and check idling RPM.
(e) Keep your left foot pressed firmly on the brake pedal and shift into D p\
osition.
(f) Measure the line pressure when the engine is idling.
(g) Press the accelerator pedal all the way down. Quickly read the highest line pressure when engine speedreaches stall speed.
(h) In the same manner, perform the test in R position. AT±54
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(f) Fully apply the parking brake and chock the 4 wheels.
(g) Start the engine and check idling RPM.
(h) Keep your left foot pressed firmly on the brake pedal and shift into D p\
osition.
(i) Measure the accumulator back pressure.
(j) With the conditions the same as in (h), ground the other probe of the test\
lead which has one end insertedinto the terminal SLN of the ECM harness side connector, then measure the accumulator back pressure
again.
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OKNG
OKNG
OKNG
INSPECTION PROCEDURE
1Main throttle position signal check.
C
OK
Hint
PTurn ignition switch ON (Do not start the engine).
Check voltage at the terminal T
T of the DLC2 while grad-
ually depressing the accelerator pedal from the fully
closed position to the fully opened position.
Voltage changes from 0 V to 8 V by stages.
Do not depress the brake pedal during this test. The
voltage will stay at 0 V if depressed.
Proceed to next circuit inspection shown on matrix chart
(See page AT±66).
2Check throttle position sensor.
See engine troubleshooting section in EG section.
Replace throttle position sensor.
3Check harness and connector between ECM and throttle position sensor (S\
ee page IN±33).
Repair or replace harness or connector.
Check and replace ECM.
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AT±66BE
IN±33
WIRING DIAGRAM
Stop Light Switch Circuit
CIRCUIT DESCRIPTION
The purpose of this circuit is to prevent the engine from stalling, while d\
riving in lockup condition, when
brakes are suddenly applied.When the brake pedal is operated, this switch sends a signal to ECM. Then
the ECM cancels operation of the lockup clutch while braking is in progress\
.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
AT±108±
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