You are correctly informed that the 802 replacement for the 801 controller does not include the very useful error fault coded diagnostics unfortunately.
There is not an equivalent to the 801 supplied by Eberspacher tbh, a great shame really.
If your Airtronic is the later generation H Kit compliant heater ( H kit logo on the heater dataplate) then the Easystart Select will provide useful diagnostics, but does not include an integrated temp sensor for heater modulation (additional temp sensor install would be required) This only matters of course if you are utilising currently the temp sensor in your 801. This can be determined if you are unsure by confirming whether the grey cable is connected from the heater to the 801 at the controller plug connection.
Please let me know if I can help any further
