Decided not to go along with the 'check every second', but be somewhat
more gentle in communication by waiting for the car to ask me to say
anything ('>'). Otherwise, the OBD often doesn't respond.

Currently, it works quite well. One issue that shows still up, is that
almost all PIDs are queried - which doesn't feel right as some PIDs
should be unavailable sometimes. This results in the car often replying
'NO DATA' - and having to wait longer than necessary for new data.
Working version (finally, again :-))

Having cast aside all 'just fire message' tactics, and now gently
waiting for OBD's invite to speak, the classes work wonderfully. Now
preparing to move the sensorcontrols out into user defined classes..
(not too much experience in XAML though, so at first only trying with C#
code classes)