However, on these cars, the temp guage runs on its own sending unit. It uses one wire to the sending unit just below the intake tract. It does not get info from the ecm and has nothing to do with the temperature sending unit which is a 2 wire sensor near the thermostat. In short, these cars run on 2 temperature sending units if you have the dash guage.
If you are getting no reading, or a very low reading, and heat is hot on the coldest days, it is likely the connection at the sending unit or the sending unit itself. The sending unit is 20 bucks at the dealer, and make a new o ring connector for the sending unit.
2009 Pontiac Vibe AWD 2.4
1993 Buick Park Avenue 3800
1984 Chevrolet Citation 2.5 liter four.