DTC C1503: Traction Control System - TCS Switch Short Circuit: Condition

WARNING: This page is about a different car, the 2002 Hyundai XG350. However, it is still accessible from the selected car via links, so may be relevant.

DTC C1503 sets when Traction Control System (TCS) switch voltage is high for 60 seconds or more. Possible causes are:

TCS switch malfunction.
HECU malfunction.
Wiring harness or harness connector malfunction.