DTC P1517: TAC Module Memory Error: Description
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
The Throttle Actuator Control (TAC) module contains data which is essential for proper TAC system operation. The TAC module continuously tests the integrity of this data. When the TAC module is unable to write or read data to and from Random Access Memory (RAM) or when the TAC module is unable to correctly read data from the flash memory, or when an internal TAC module processor fault is detected, this DTC sets.