Lexus SC300 / Lexus SC400. Service manual — part 75

MEASURE ACCUMULATOR BACK PRESSURE

AT0QU–01

NOTICE:

Perform the test at normal operating fluid temperature 50–80

C (122–176

F).

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 rear right side and connect the oil pressure gauge SST.

SST 09992–00094

HINT: Connecting the oil pressure gauge will be made easier by moving the RH side head insulator aside.

(c) Remove the passenger side No.2 under cover and ECM protector.
(d) Connect the SST (check harness A) between ECM and connector of vehicle wire harness.

SST: 09990–01000

(e) Install one test lead probe into the terminal SLN of the ECM wire harness side connector and take care

not to ground the other test lead probe.
HINT: Prepare test leads which are connected with an (approximately) 8 W light bulb.

AT–56

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

(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 position.
(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 inserted
into the terminal SLN of the ECM harness side connector, then measure the accumulator back pressure
again.

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

AT–57

SPECIFIED ACCUMULATOR BACK PRESSURE

ÑÑÑÑÑÑÑÑÑÑÑ

Condition if ECM terminal SLN

ÑÑÑÑÑÑÑÑÑÑÑÑÑ

Not ground kPa (kgf/cm

, psi)

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Ground kPa (kgf/cm

, psi)

ÑÑÑÑÑÑÑÑÑÑÑ

Accumulator back pressure

ÑÑÑÑÑÑÑÑÑÑÑÑÑ

177–255 (1.8–2.6, 26–37)

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

EVALUATION

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Problem

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Possible cause

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Throttle cable out of adjustment

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

l t

ifi d

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Throttle valve defective

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

The accumulator back pressure is not as specified
(high or low) when the terminal SLN is not ground.

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Solenoid modulator valve defective

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

(high or low) when the terminal SLN is not ground.

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

SLN solenoid valve defective

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Accumulator control valve defective

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

The accumulator back pressure does not become 0
kgf/cm

when the terminal SLN is grounded.

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

SLN solenoid valve defective

AT–58

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

MANUAL SHIFTING TEST

AT0QV–01

HINT: With this test, it can be determined whether the trouble
is within the electrical circuit or is a mechanical problem in the
transmission.

DISCONNECT SOLENOID WIRE

INSPECT MANUAL DRIVING OPERATION
Check that the shift and gear positions correspond with the
table below.

ÑÑÑÑÑÑÑÑÑÑÑ

Shift Position

ÑÑÑÑÑÑÑÑÑÑÑÑ

Gear Position

ÑÑÑÑÑÑÑÑÑÑÑ

D Position

O/D

ÑÑÑÑÑÑÑÑÑÑÑ

2 Position

3rd

ÑÑÑÑÑÑÑÑÑÑÑ

L Position

1st

ÑÑÑÑÑÑÑÑÑÑÑ

R Position

Reverse

ÑÑÑÑÑÑÑÑÑÑÑ

P Position

Pawl Lock

HINT: If the L, 2 and D position gear positions are difficult to
distinguish, perform the following road test.

•

While driving, shift through the L, 2 and D positions.

Check that the gear change corresponds to the shift
position.

If any abnormality is found in the above test, the problem is
in the transmission itself.

CONNECT SOLENOID WIRE

CANCEL OUT DIAGNOSTIC TROUBLE CODE
(See page AT–39)

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

AT–59

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Lexus SC300 / Lexus SC400. Service manual — part 75

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