2001 Lexus RX300 Question: sensor lights on dash

The rear lights malfunction light (little yellow icon) comes on when a bulb failure is experienced check all the lights and brake lights including the 3rd brake light. Replace the defective bulb turn off the ignition key and restart the vehicle that light should go off. The $1100 repair I suspect was for a evaporative emission canister replacement and diagnostic work but you would have to check your repair order. I have seen Oxygen sensor heater failure as well (O2) but should have been less expensive.
The sensors cannot be disconnected that alone would turn on the light and it is illegal to tamper with emission control devices. You need to have the computer on your car scanned for faults, if you can tell us the trouble codes ie PO420, or P1234 we can tell you what is most likely wrong. I work on a lot of theses cars they are very good and reliable, apart from a couple of small things.