I'm looking at a '02 Firebird engine coolant temperature sensor/sender wiring diagram, and what's the difference between low reference & ground? For example, a '02 ECT sensor has 5V Reference and Low Reference (both to PCM), whereas the '98 ECT sensor has a 5V Reference and Ground (both to PCM) plus a third wire for the gage.
The Low Reference is ideally "ground", but it is meant to
be free of any current-loop offsets such as you would
have in an engine block, ground strap, body sheet metal
involved path. Different reading with headlights on and
off, etc., would be bad sometimes. They use it for the
fussier / more critical sensors to take out these kinds of