Lexus SC300 / Lexus SC400. Manual — part 87

OK

NG

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check voltage between terminal KD of ECM connector and body ground.

C

OK

P

1.

Connect the check harness A to the ECM (See EG
section).

2.

Turn ignition switch ON (Do not start the engine.)

Measure voltage between terminal KD of ECM connec-
tor and body ground when accel. pedal is fully de-
pressed or not.

Proceed to next circuit inspection shown on matrix chart
(See page AT–66).

2

Check kick–down switch.

C

OK

1.

Disconnect dick–down switch connector. (See
page AT–18)

2.

Measure resistance between terminals 1 and 2 of
kick–down switch connector when kick–down
switch is ON and OFF

Replace kick–down switch.

3

Check harness and connector between ECM and kick–down switch, kick–down switch and
body ground (See page IN–33).

Repair or replace harness or connector.

Check and replace ECM

–

A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

AT–105

The park/neutral position switch detects the shift lever
position and sends signals to ECM.The ECM receives
signals (R, PNP, 2 and L) from the park/neutral position
switch. When the signal is not sent to the ECM from the
park/neutral position switch, the ECM judges that the
shift lever is in the D position.

AT–66

IN–33

WIRING DIAGRAM

Park/neutral Position Switch Circuit

CIRCUIT DESCRIPTION

DIAGNOSTIC CHART

DIAGNOSTIC CHART

AT–106

–

A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

OK

NG

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check voltage between terminal R, PNP, 2, L of ECM connector and body ground.

C

OK

P

1.

Connect the check harness A to the ECM (See EG
section).

2.

Turn ignition switch ON.

Measure voltage between terminals R, PNP, 2, L of
ECM connector and body ground when the shift lever is
moved to the following positions.

*: The voltage will drop slightly due to lighting up of the
back up light.

Proceed to next circuit inspection shown on matrix chart
(See page AT–66).

2

Check park/neutral position switch.

C

P

1.

Jack up the vehicle.

2.

Remove park/neutral position switch (See page
AT–18).

Check continuity between each terminal shown below
when the shift lever is moved to each position.

Replace park/neutral position switch.

3

Check harness and connector between ECM and park/neutral position switch, park/neutral
position switch and battery (See page IN–33).

Repair or replace harness and connector.

Check and replace ECM.

–

A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

AT–107

AT–66

BE

IN–33

WIRING DIAGRAM

Stop Light Switch Circuit

CIRCUIT DESCRIPTION

The purpose of this circuit is to prevent the engine from stalling, while driving 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 CHART

DIAGNOSTIC CHART

AT–108

–

A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING