Cadillac 2008 XLR Owner's Manual page 54

If the on indicator is still lit, do not install a child restraint
in this vehicle and check with your dealer/retailer.
The passenger sensing system is designed to enable
(may inflate) the right front passenger's frontal airbag
and seat-mounted side impact airbag anytime the
system senses that a person of adult size is sitting
properly in the right front passenger's seat. When the
passenger sensing system has allowed the airbags
to be enabled, the on indicator will light and stay lit to
remind you that the airbags are active.
For some children who have outgrown child restraints
and for very small adults, the passenger sensing
system may or may not turn off the right front
passenger's frontal airbag and seat-mounted side
impact airbag, depending upon the person's seating
posture and body build. Everyone in your vehicle who
has outgrown child restraints should wear a safety
belt properly — whether or not there is an airbag for
that person.
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If a person of adult-size is sitting in the right front
passenger's seat, but the off indicator is lit, it could be
because that person is not sitting properly in the seat.
If this happens, turn the vehicle off, remove any
additional material from the seat, such as blankets,
cushions, seat covers, seat heaters or seat massagers
and ask the person to place the seatback in the fully
upright position, then sit upright in the seat, centered on
the seat cushion, with the person's legs comfortably
extended. Restart the vehicle and have the person
remain in this position for two to three minutes.
This will allow the system to detect that person and
then enable the right front passenger's frontal airbag
and seat-mounted side impact airbag.