How many miles on it ? I would check if all brake lights operate properly, and maybe have a look at the brake pedal switch. May as well get the battery voltage - disconnect after driving then wait 1 hour. If it's lower than 12.2v I would replace it

 

Hello,

114.000 miles.
I checked the brake light. It works well. The switch in the parking brake works but when I release the switch buzzing in the speaker increases, When I push the switch buzzing decreases.
By the way, I followed your suggestion. Just after I parked my car, I disconnected the battery from both terminals and measured the voltage. It was 12.8V then i left it like that for like 4 hours. Then I measured again it was 12.78V.

 

I scanned with 3 different OBD2 Readers but there is no error code.

There is no error code, or is the tool perhaps unable to communicate with the ABS module?
Generic OBD2 readers are unable to communicate with the ABS. They are only capable of diagnosing engine problems. You need a more advanced scan tool to diagnose ABS/ESC issues.

The mechanic says the lights are on with no error code because there is a communication problem between the ABS control unit and the main computer.

A communication problem would log a trouble code though. But if the "main computer" is unable to communicate with the ABS module the mechanics scan tool wouldn't be able to either. It's connected to the same data bus.

If I helped you fix it, why not...

Your support is greatly appreciated​

 

What kind of mechanic is that, talking BS about a mysterious 'main computer' ??? HAL 9000 ?

@OP: there is plenty of scantools for less than 100$ that can do OBD2 (which is a purely emissions related standard) and more things like ABS/TCS 'n stuff and SRS. E.g. from Topdon or Autel.
The oul' ELM327 for 10$ can only do OBD2 ...

Battery/alternator is generally a good guess, but even then there will be a code set.

 

Hello,
first, I scanned with my scanner which cost around $20. No code.
Then I went to Autozone. They scanned. No code.
Then I went to the mechanic. He scanned. No code.
The OBD2 readers in Autozone and the mechanic has look fancy but I do not know the brand or model.

To me, if there is a warning on the dashboard there should be a code too. Because the car is warning us.

 

This is how we access codes at Hyundai dealer.

Select "ALL", and scan everything in 1 shot, print ACTIVE & HISTORY screenshots

 

This is how we access codes at Hyundai dealer.

Select "ALL", and scan everything in 1 shot, print ACTIVE & HISTORY screenshots

Does Hyundai dealer charge you, if you only want to scan?
Thank you.

 

12.8V is excellent,
the brake switch is actually activating some modules, on top of the rear brake lights. Maybe one of these has an electric issue, causing that speaker buzz. I'm not aware which modules, but worth finding out and looking at the fuses for these modules.