Low coolant temp

[asshanson]

Emily's 2001 zx2 just had the CEL go on the other day, and a couple days before I noticed coolant temp on the gauge would take forever to get up past cold, and barely even makes it to the normal "warm" point if you're idling in traffic. As soon as you hit the interstate it goes back down a little closer to cold.

I checked the obd2 logger and it said it couldn't warm up enough while in closed loop mode.

So I'm thinking either bad coolant temp sensor or stuck open thermostat. What do you guys think given the symptoms? Yes the car has enough coolant.

My first guess was coolant temp sensor, but do those start to go bad and just read low? Or do they go out completely and read way off?