It’s sounds like your code reader is not communicating with the ECU (where the codes are stored). If yo uhave another code reader, try that to see if you get the same message. If you do get the same message, you may (I stress MAY) have an issue with your ECU. The early Quests (2004-05) had an issue with the placement of the ECU exposing it to rain and causing them to prematurely fail due to rust. If you do a quick search on this forum, you will find a number of people complaining.
ONe member posted detailed instructions on how to protect this from happening. Those instructions give very detailed information on the location of the ECU (Passenger side, near the firewall) and how to check it.
Note: it should be ECM not ECU.