You need free software and a windows laptop to read these codes. You may be able to find it on the web. You're looking for a file titled EVOLUTION Service Tool R2.exe. You can download it from this website (Windows 10 is required).

Connect USB cable from the APU motherboard to USB in your laptop and run the software.

Code 31. Check oil pressure switch

Code 35. Check Run Relay.

Code 49. Restricted air flow.

Code 249. Engine coolant sensor (WT1)

Thermo King TriPac Evolution APU Error Codes