On a 2003 Sonata car, is the brake monitoring system. a part of the yellow engine light?
Brake monitoring indication should not be mixed with other or combined with other parameters and should be separated in the dashboard with clear vision to the driver as per safety norms. In case where space constrain is there, risk involved while noticing the indication and in that case audio is also necessary
If there isn't a dedicated separate warning indicator for the brakes and ABS system then yes. It can also trigger an alarm light if the brake fluid level gets too low in the reservoir.