same here... but I noticed he was not confident in his answer, to replace sensor. It all happened all of sudden, was working fine and one day I noticed light is on! Same with TPM I could clear it for few times and now it does not go off.

 

try disconnecting and reconnecting all the plugs under the seats a few times. that fixed the problem i had.

 

Already great posts, like mentioned above, if the plugs under the seat come undone it can cause this.
I found out by accident when I pulled the passenger front seat to run wires for a stereo and forgot to hook up a plug.

>> On the RX330, RX400, and maybe the RX350 too, the "occupant classification" weight sensors and seat belt(buckle switches) are directly wired to the Occupant Classification ECU.
>> The Occupant ECU is hooked up to the Airbag Sensor Assembly ECU.
>> The Airbag Sensor Assembly ECU is what turns on the airbag warning lights the best I can tell.

So, using techstream looks to be the fastest way to troubleshoot but I wouldn't be happy paying someone $150 to spend 5 mins to hook it up and verify an unresponding sensor and shrug their shoulders and tell me nothing after I just paid for an hour of work.

Can I please add, because of the complexity of these circuits I'm guessing only the dealer or an indy with an electrical specialist on staff can go very deep into this job if it requires more than simple wire/plug chasing or sensor replacement. A chain store or general repair shop has little chance unless someone like Scanner Danner works there. lol

 

If only every shop had a Scanner Danner!