07 ion 2.2 po128 coolant temp below thermostat reg temp

your car has to run at certain temp for optimum fuel economy and for optimum performance, if it gets out of the peramiters it will set the code, You need to change the thermostat that will fix your problem

This code is telling you the thermostat needs to be replaced. Another thing associated with this would be the temperature sending unit. The coolant would be drained down anyway so it would be a good idea to change both. Yes this affects the ecm in adjusting the other sensors on the motor,

the thermostat is fine the question was if the gauge doesn't work will it kick that code

Yes it would but then the question is why is the gauge not working? The temperature sending unit is the main key for what information the ecm sends to the other sensors. Also first check to see if there is a fuse that is blown.

final got around to fixing problem.1st checked to see if sensor was bad by unplugging wiring harness and jumping 1 wire to the other with a paper clip.With key on and wires jumped gauge didn't move.Sensor was not the problem.More dia. realized fan also ran all the time.long story short pulled thermostat was very noticable t-stat was coming apart and sticking open.Replaced t- stat fix gauge problem and po128 code thanks for your help