Passenger seat belt warning stays on even with ignition off

Audible Warnings Description
The seatbelt/ ignition key/ lamps alarm provides an audible warning for the following signals:
• The fasten seat belt reminder
• The key in the ignition reminder
• The headlamps ON reminder

Seat Belt/ Ignition Key/ Lamps (Warning) Alarm
Behind the instrument panel, on the right side of the A/C module

Looks like it has several connectors to it, just pull the one connector to stop the chime (warning) your hearing. Assume you have one on all the time? annoying isn't it .

These two faults maybe unconnected. Starting with the seat belt warning. There should be a switch in the seat to check if someone is sitting in it and a switch in the seat belt catch to check if the seat belt is engaged. If either of these switches or the wiring to them is faulty then the light will come on if the ignition switch is turned on. The airbag warning will come on if there is a problem with the explosive that operates the bag or wiring to it. I would check under the front seats of your car for wiring damage or a not fully engaged plug and socket. These can be damaged or work loose if things have been pushed under the seats.

This may or may not be the problem , so watch some other heated seat repair videos How to Fix Broken not working seat Heater 2003 10 Cadillac CTS CHEVY GMC SEAT HEATER TROUBLESHOOTING YouTube

Could be a problem with the sensor in the seat. The system thinks someone is sitting in the seat and the seat belt is not fastened.

2005 Cadillac SRX Disappearing Third Row MAGIC seat at Trend Motors Used...

Remove the rear lower seat. Remove bolts holding belts to floor pan of vehicle.

Pull the fuse it won't affect the seatbelts from working correctly. otherwise you have to disconnect each seatbelt lock to find the defaulted lock. As for the airbag light; do you have the type that can be turned off with a key? It may be permanently turn off and needs to be turned back on with the key.

The Body Control Module (BCM) controls the audible warnings. Refer to Body Control System Description in Body Control System for more information regarding the BCM.
The body control module (BCM) controls these reminders:
• Key in ignition reminder: An audible warning intended to remind the driver that the key has been left in the ignition cylinder. The BCM sounds the chime for this reminder at a rate of 150 chimes per minute.
• Fasten seat belt reminder: An audible warning intended to remind the driver at the beginning of the driving cycle that the driver's seat belt is unfastened. The BCM sounds the chime for this reminder at a rate of 50 chimes per minute.
• Fasten belts indicator control: A visual warning intended to remind the driver that the driver's seat belt is unfastened.
• Parking brake reminder: An audible warning intended to remind the driver that the parking brake has been left applied with the transaxle shifted out of PARK. The BCM sounds the chime for his reminder at a rate of 200 chimes per minute.
• Turn signal reminder:
An audible warning intended to remind the driver that the turn signal has been left on while the vehicle has traveled over 1.2 km (¾ mile). The BCM sounds the chime for this reminder at a variable rate (in unison with the turn lamps on) of 90 chimes per minute.
• Headlamps ON reminder: An audible waring intended to remind the driver that the headlamps have been left on. The BCM sounds the chime for this reminder at a rate of 200 chimes per minute.
• Last door closed locking confirmation: An audible warning intended to provide the driver feedback that the last door closed locking feature is active. The BCM sounds the chime for this remainder at a rate of 200 chimes per minute.
• Feature customization and diagnostics feedback: An audible feedback used when changing feature customization modes. Also used by service technicians during the BCM diagnostics. The BCM sounds the chime during the feature customization, and also during diagnostics. Refer to Body Control Module (BCM) for additional information.

Step
Action
Value(s)
Yes
No
1
Was the BCM diagnostic system check performed?
--
YES - Go to Step 2
NO - Go to Diagnostic System Check - Body Control System in Body Control System
2
Check for Powertrain Control Module (PCM) Diagnostic Trouble Codes (DTCs). Refer to Powertrain On Board Diagnostic (OBD) System Check (LX5) or Powertrain On Board Diagnostic (OBD) System Check (L36) in Engine Controls for more information.
Are there any PCM DTCs present?
--
Go to Appropriate DTC Table in Engine Controls
Go to Step 3
3
Connect a scan tool to the Data Link Connector (DLC).
Using scan tool, select BCM data display inputs and monitor the park brake switch input.
While observing the scan tool, apply and then release the park brake.
Does the scan tool indicate that the park brake input is off while the park brake is released?
--
Go to Step 7
Go to Step 4
4
Turn the ignition switch off.
Disconnect the scan tool from the DLC.
Disconnect the BCM connector C1.
Release the park brake.
Using a test light, connect between B+ and the BCM connector C1 terminal D5.
Is the test light off?
--
Go to Step 7
Go to Step 5

Your best bet ,take it to a qualified repair shop

It's approximately $350 as you were told even though you can see it lower. be sure to let it be fitted at a toyota garage.

Do rate this....

I have found that it does this when someone has been riding then I get out of the car without me putting it in park after, so I put car in park and reopen then close door and it goes off