Lexus SC300 / Lexus SC400. Manual — part 174

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Parts Name

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Function

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Passenger’s Seat
ECU

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The passenger seat ECU controls the distance the seat slides when the power seat switch is
operated and also controls the power slide distance during return operation.

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Power Seat Switch

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When the power seat switch is operated, a seat slide signal is sent to the ECU. The reclining
slide of the switch is linked directly to the motor operation.

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Slide Position Sensor

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The slide position sensor detects the slide distance during walk–in operation and
inputs the information to the ECU.

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Slide Neutral Limit
Switch

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This switch detects the neutral position of the seat slide and input the information to the ECU.

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Reclining Front Limit
Switch

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This switch detects when the seatback is inclined fully forward and informs the
ECU.

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Reclining Rear Limit
Switch

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This switch detects when the seatback is pulled back and informs the ECU.

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Motor

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There are two motors, one each for seat sliding and for reclining.

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Tension Reducer and
Buckle Switch

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This switch inputs a signal to the ECU to inform it whether the tongue of the
passenger’s seat belt is inserted in the buckle.

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BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

BE–311

PARTS LOCATION

BE–312

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BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

HOW TO PROCEED WITH TROUBLESHOOTING

Perform troubleshooting in accordance with the procedure on the following page.

CUSTOMER PROBLEM ANALYSIS

Using the customer problem analysis check sheet for reference, ask the customer in as much detail as
possible about the problem.

PROBLEM

SYMPTOM

CONFIRMATION,

SYMPTOM SIMULATION.

Confirm the problem symptoms. If the problem does not reappear, be sure to simulate the problem using
the ”Problem Simulation Methods”.

MATRIX CHART OF PROBLEM SYMPTOMS

Confirm the order of inspection on the matrix chart for the particular problem symptom involved. For ”Not
Functioning” problems, pay attention to the points in

to find out the specifics of the problem, then choose

the most appropriate problem symptom from among those listed on the matrix chart, and proceed with trou-
bleshooting accordingly.

CIRCUIT

INSPECTION

Proceed with diagnosis of each circuit in accordance with the inspection order confirmed in

. Determine

whether the cause of the problem is in the sensor, actuators, wire harness and connectors, or the ECU.

POSITION SENSOR CHECK

This function checks that the signal from position sensor is correctly input into the ECU. The instructions
for this diagnosis are included in the flow chart for the position sensor circuit.

REPAIR

After the cause of the problem is located, perform repairs by following the inspection and replacement pro-
cedures is this manual.

CONFIRMATION

TEST

After completing repairs, confirm that the problem is eliminated and power walk–in operation is normal.

BE–314

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BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)