With the sensor plugged in I get 13.8v on the voltage supply wire to the heater element, but only a trace (.43v) when I put the meter between it and a ground.

I know you know what you said here, but I'm not sure. Can you be a little more explicit?

With the sensor unplugged I do not get continuity between the two wires but rather a reading of 6.7ohms (misplaced decimal??)

Measuring the resistance of the heater immediately after disconnecting it from a cold engine (but heater warmed for a minute) is the best way to determine its goodness. 6.7 ohms is a reasonable reading. For example, I will see about 14 ohms while the heater is still hot, and be able to watch it cool down to about 4 to 5 ohms, per my level of patience. Doing this on a hot motor will lengthen the time a little due to residual heat in the cat.

Watching it cool not only convinces you it has been heated (electrically) but that it does not open up at some particular temperature because of a cracked connection or element.
--
Art Benstein near Baltimore

A Stranger is just a friend you haven't met yet.