Engine/Transmission (1994 - 1998) -40 Engine temp Reading?

[DonFitzwater]

I've got a Matco diagnostic scanner that reads -40 degrees while it's hooked up to my 1997 12 valve. All of the other functions seem to be correct except the engine coolant temp... ... is this a default setting for some reason? Got around 180 on the dash mounted guage and a hand held shows 190 at the t'stat housing. ??????????????