What does Error Code 2502 indicate on the PURY-HP72 and where can I find the troubleshooting steps?

Error Code 2502 falls within the 2000-2999 range of error codes covered in Chapter 7 of the service manual. Definitions and solutions for codes in this range are detailed in section 7-4, Error Code Definitions and Solutions: Codes [2000 - 2999]. Refer to that section for the specific cause and corrective action for this error. (Page 184)