[JFP in PA]

Then it is working and the wiring is fine, with the exception of the fact the DME is not always seeing it working.

I would take a close look, as in manually tracing it, at the harness from the sensor to the DME; there are often multiple connectors in these harnesses, one or more of which may be loose or show terminal corrosion which could be the cause of your intermittent issue.