From the owner's manual on my 2004 RX330:
If an adult sits in the front passenger seat, the “AIRBAG OFF”
indicator may also be illuminated if the following occurs.
- The rear passenger lifts the front passenger seat cushion with their legs.
- Objects are placed under the front passenger seat.
- A front passenger seat seatback is in contact with a rear seat.
To ensure the system correctly detects an adult sitting in the
front passenger seat, make sure the above do not happen.
Make sure the “AIRBAG OFF” indicator light is not illuminated
when an adult sits in the front passenger seat. If the “AIRBAG
OFF” indicator light is illuminated, ask the passenger to sit up
straight, well back in the seat, and with the seat belt worn
correctly. If the “AIRBAG OFF” indicator light still remains
illuminated, either ask the passenger to move to the rear seat,
or if that is not possible, move the front passenger seat fully
The “AIRBAG OFF” indicator light will be initially
illuminated when the ignition switch is turned to the “ON”
position. It will remain for about four seconds and then go
off. After about two seconds, the front passenger
occupant classification system operates and judges
whether to turn the indicator light on or not.
The SRS warning light and “AIRBAG OFF” indicator light
will be illuminated if there is a malfunction in the front
passenger occupant classification system.