1998 XJ8 VdP. Anyone know what this is?

 

P1111 means all checks are completed. So you should be good.

 

Thanks, Norri!

Some electronic gremlins I know the car has: heater sometimes goes cold, then goes hot again; seat memory buttons work intermittently; rear right side electric window does not work (probably a busted motor). Thanks in advance for anymore insight...

 

Three possibilities come to mind on the heater:

1) The in cabin temperature sensor has a litle fan to circulate air to it. Se archives for th elocation under the dash. Take the cover off and clean the lint out.
2) The heater valve is sometimes reported to stick. (the thing just fron of the firewall with 4 heater hoses. It powers on to close. So, take it's connector loose and see if the heat stays on.
3) The heater aux electric pump, just in front of the heater valve can be failing. New ones are big $, so maqny of us have gotten replacement brushes from a small motor shop and files and sanded then]m to fit.

Just to say the obvious, make sure your coolant ids full!