Lexus ES300 2003 Manual page 128

COMFORT ADJUSTMENT
Front seat belt pretensioners
The driver and front passenger's seat belt pretensioners
are designed to be activated in response to a severe
frontal impact.
When the airbag sensor detects the shock of a severe frontal
impact, the front seat belts are quickly drawn back in by the
retractors so that the belts snugly restrain the front seat
occupants.
The front seat belt pretensioners are activated even with no
passenger in the front seat.
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This indicator comes on when the ignition key is turned to
the "ON" position. It goes off after about 6 seconds. This
means the front seat belt pretensioners are operating
properly.
This warning light system monitors the airbag sensor
assembly, front airbag sensors, side and curtain shield airbag
sensor assemblies, curtain shield airbag sensor assemblies,
driver's seat position sensor, driver's seat belt buckle switch,
front seat belt pretensioner assemblies, inflators, warning light,
interconnecting wiring and power sources. (For details, see
"Service reminder indicators and warning buzzers" on page 50
for instructions.)