Lexus ES300 (1997 year). Service manual - part 23

90

BODY — ENHANCEMENT OF PRODUCT APPEAL

ENHANCEMENT OF PRODUCT APPEAL

 WINDSHIELD MOULDING

A rain gutter has been incorporated into the periphery of the windshield moulding in order to reduce the rain
flow down from the roof panel to the windshield glass.

 DOOR LOWER MOULDING

A door lower moulding has been provided below the outside moulding to prevent the top of the rocker panels
from getting soiled. This prevents the passengers’ clothes from getting dirty when entering and exiting the
vehicle.

91

BODY — SEAT BELT PRETENSIONER

SEAT BELT PRETENSIONER



 DESCRIPTION

A mechanical sensing type seat belt pretensioner is incorporated with the front outerside seat belt.
In a collision, the pretensioner sensor detects the shock and if the front-to-rear shock is greater than a
specified value, the seat belt pretensioner is activated instantaneously to pull in a predetermined length of
the seat belt.

— REFERENCE —

The mechanical sensing type seat belt pretensioner is equipped with an independent pretensioner sensor.
For this reason, depending on the circumstances of the collision, the seat belt pretensioner may not operate
when the airbag is deployed, and vice versa. The same is applied between the right and left seat belt
pretensioners.



 CONSTRUCTION AND OPERATION

1. General

The seat belt pretensioner consists of the pretensioner mechanism, retractor mechanism, and ELR locking
mechanism. The pretensioner mechanism consists of a pretensioner sensor, gas generator, cylinder, etc. The
pretensioner sensor detects the vehicle’s deceleration speed during a collision.
In addition, a safety device is installed to prevent the seat belt pretensioner from being activated by the seat
belt retractor assembly alone.

92

BODY — SEAT BELT PRETENSIONER

2. Gas Generator with Pretensioner Sensor

The pretensioner sensor consists of a inertial mass, trigger shaft, firing pin, firing spring, etc.
The trigger shaft and the firing pin are normally engaged with each other so that the firing pin is not ejected.
In addition, if any unnecessary inertial mass movement is suppressed by the bias spring force, the seat belt
pretensioner is not activated by mistake.
If a severe frontal collision occurs, the vehicle decelerates instantaneously. The inertial mass begins to move
despite the bias spring force. If rapid deceleration continues, the spring force of the firing spring disengages
the firing pin from the trigger shaft, ejects the firing pin, and ignites the primer. The flame spreads
instantaneously to the gas generator and a large amount of gas is generated from the gas generator.

 Non-Deployed State 

 Deployed State 

3. Pretensioner Mechanism

When the pretensioner sensor comes on, the gas generator emits gas in an extremely short time and pushes
the piston. Since the cable is attached to the piston, the piston will pull on the cable causing the drum to grab
onto the shaft. The shaft will then move in the retracting direction taking up the belt for a predetermined length.

93

BODY — SEAT BELT PRETENSIONER

4. Safety Device

To activate the safety device, the sensor lock button illustrated below must be pressed with a flat-blade
screwdriver or an equivalent tool, which causes the sensor lock release lever to push out and turn 90



clockwise. As a result, the trigger shaft becomes fixed and stops the operation of the seat belt pretensioner.
To release the safety device, rum the sensor lock release lever counterclockwise and press it in.

 Safety Device Active 

 Safety Device Released 

Service Tip

During the installation of a seat belt pretensioner onto the vehicle, if the safety device is active, the
sensor lock release lever and center pillar garnish infringe upon each other and will prevent the center
pillar garnish from attaching. This prevents the technician from forgetting to release the safety device.