2002 Bonneville 130k miles

Light has gone on a couple of times. First time I reset the light to see if it came back, it did. The code reads something about the coolant temperature.

The second time I had a coolant sending unit/sensor replaced.

The check engine light just came on again.

It is probably coincidence but each time the light has came on when I am getting low on fuel.

Any thoughts or do you need the exact code?

A specific code would most definitely be the best. Otherwise, any opinions will just be speculation.

How cold is it outside when the light comes on?
How is the cars interior heater working, plenty of warm air?

The outside temp has probably been in the 30'* and yes, the heater works just fine. The mechanic asked the same question after reading the scanner.