Lexus ES300 (1997 year). Service manual - part 28

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4. Construction and Operation

Inflator and Bag for Front Passenger

1) Construction

The inflator is comprised of a squib, projectile, orifice disk, propellant grain, high pressure argon gas and
etc. The bag is made of strong nylon cloth, and becomes inflated by the argon gas generated by the inflator.
The inflator and bag are integrated inside the case, and located in the passenger side instrument panel.

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2) Operation

If the airbag sensor is activated by deceleration due to frontal collision, the electric current then ignites the
squib located in the inflator. The projectile which fired by the ignition of the squib pierces through the orifice
disk and collides with the action piston, which causes the primer to ignite. The flame of the primer spreads
instantaneously to the ignition booster and to the propellant grain. The gas which expanded by the heat of
the ignition of the propellant grain flows into the airbag via the gas release hole, thus inflating the airbag.
The airbag pushes the airbag door open to further expand and to help restrain the impact applied to the head
and chest of the front passenger.

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 CRUISE CONTROL SYSTEM

1. General

Once the system is set to a desired vehicle speed, the engine throttle position is adjusted automatically to
maintain the vehicle speed at that speed without depressing the accelerator pedal.
The basic construction and operation of this system are the same as in the previous model. However, on
the new model, the control method for the manual and auto cancel functions have been changed. Also, a
new motor type actuator that is both lightweight and simple in construction has been adopted.

2. Construction and Operation

Actuator

The new ES300 has adopted a new motor type actuator. The new motor type actuator consists of a motor,
control link and limit switch, etc. as shown below.
The potentiometer that measured the opening angle of the control link and transmitted the signals to the
cruise control ECU has been discontinued in the new actuator. The new actuator is equipped it with a
compact motor. As a result, the new actuator is made both lightweight and simple in construction. Without
the potentiometer, the new actuator continuously regulates the opening angle of the control link. This is
made possible by the ECU, which compares the current vehicle speed input with the desired vehicle speed
that is stored in memory, and the result of that comparison is transmitted to the actuator.

Cruise Control ECU

1) Manual Cancel Function

The manual cancel function has been changed as follows:

New

Previous

Transaxle shifted to positions other than “D”.

Transaxle shifted to “N” position.

—

Pull up the parking brake lever.

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2) Auto Cancel Function

When the vehicle is being driven under cruise control, if any of the conditions listed below is present, the
vehicle speed stored in memory is deleted, the control is lifted, the current to the actuator is disrupted, and
the power indicator light is made to flash. The methods to reactivate the cruise control at that time, in
accordance with that particular condition (malfunction category A or B), are classified in the chart below.
Other auto cancel functions are basically the same as those of the previous model.

Condition

Malfunction

Category

How to reactivate

 Continuous current applied to the motor’s

acceleration output.

 The motor did not move.

A

Turn off the ignition switch, and
turn it back on. Then turn on
the main switch.

 Excessive current flowed to the motor or

magnetic clutch drive transistor.

 Open circuit in magnetic clutch.

(Includes a blown stop light fuse.)

 The vehicle speed signal is not sent for a

predetermined period of time (approx. 140
reset.)

 The vehicle speed is equal to the set speed

minus approximately 16 km/h (10 mph) or
below.

 Short circuit in the control switch.
 Open circuit in deceleration control.

(Including an open circuit in the motor.)

B

Turn the main switch back on.

3) Diagnosis Function

a. Warning Indication

The cruise control ECU immediately blinks the power indicator light in the combination meter on and
off repeatedly to alert the driver of a system malfunction.
When the power indicator light is flashing, and the cruise control is released by pressing on the main
switch, the power indicator light will be turned off. When the main switch is turned back on, and cruise
control driving is resumed, the power indicator light output pattern, as shown on the next page, differs
according to the malfunction categories A or B. When a category A malfunction is occurring, the power
indicator light will flash again, but if it is a category B malfunction, the indicator light will remain on,
indicating that the system is operating.