I have one with the same fault. It works for 2 mins then beeps and gives the error message. There is no mention of error codes in the manual that comes with it.
Wills
August 2011
Check the troubleshooting section of your manual.
If google and manufacturer website are of no help then ask a manual search agency like http://manualfox.com/link/goodmans.htm - They can get you every Goodmans manual.