Toyota Repair: 98 toyota avalon brake light indicator, toyota avalon, volt ohm meter

Question
I have a 98 Toyota Avalon & the brake light indicator is on my dash board but all of my brake lights are working properly so im really confused as to what it could be I called the Toyota dealership & they said they would have to run a $120 diagnostic test on it to figure out the problem which I feel is ridiculous they just want a lot of money for something that could be simply fixed & I was also told that it could be a light bulb that isn't the right bulb in my lights but im not sure what to do. Please help!

Answer
The warning light can turn on in some cases due to the wrong bulb or a bulb that has too much resistance and may have been overheated, this is common, I would recommend that you replace all the stop light bulbs including the one on the rear shelf, if the problem persists please reply back and we can go from there, in case we do it would help if you have a volt/ohm meter.