DTC C1503-01: TCS Switch Error: General Description
WARNING: This page is about a different car, the 2018 Hyundai Accent. However, it is still accessible from the selected car via links, so may be relevant.
A driver can control the ESC system by the ESP OFF switch.
When the switch signals to the ESP (ESC), the ESC warning lamp will go "ON" and the ESC control will stop. If the driver hits the switch again, the ESC control will be back on. This function is used for sporty driving or vehicle inspection.