Can you tell me what this code is? A893
I shut the furnace off to change the filters and when I switched it back on the first code was A444. I then raised the temperature to see if the furnace was working, it was, but now the code shows A893. Do you know what this is?

They are not error codes. If you look at this link, you will see that they are diagnostic codes for stage and air flow.
Lennox G71MPP error codes ??? (http://hvac-talk.com/vbb/showthread.php?310302-Lennox-G71MPP-error-codes).
A stage heating, 893 CFM air flow.

It means the system is gearing up to deliver heat. Here is a manual for future reference.

https://www.manualslib.com/manual/1077404/Lennox-G71mpp-Series.html