I hope not. I think whiskeywarden is referring to the MAF/IAT sensor at the air cleaner assembly that looks like:

 

This is exactly what I am looking at. Is that the wrong thing?

As for the P0128 code. I did change the thermostat from what looked like the original to a new 195 deg thermo. but the temp still only gets to 1/2 way between 1/4 and 1/2 on the temp gauge. I am a novice backyard mechanic and if I know what to do I do it but I am not great on diagnosing things.

 

My apologies, I forgot about the MAF sensor. I saw the word "flap" and instantly thought of the throttleplate.

The temp gauge is reading the normal operating temp so the thermostat is probably fine. FWIW our Equinox has never reached the 1/2 mark in the 3 years we've owned it - it only gets to about the 3/8 area between the 1/4 and 1/2 marks just like you described.

The engine computer compares the IAT (Intake Air Temperature) sensor reading to that of the ECTS (Engine Coolant Temp Sensor) during a cold start as part of the criteria for P0128, so if the IAT sensor part of the MAF sensor is not working it may cause a P0128. The P0100 code may be programmed to be flagged in this scenario rather than a normal IAT related code since the IAT sensor is integrated into the MAF sensor and not a separate part. The computer is unable to determine which sensor is bad because it only has the readings from these two sensors to compare to each other to use as relevant data. Since the temp gauge seems to be working fine, this means the IAT sensor is probably not working.

If all the wiring checks OK, then I'm thinking a new MAF sensor might be the fix at this point. You could pull the ECM/TCM 10A fuse for 30 seconds to clear the codes, and wait to see what comes back. However, I think the P0128 and P0100 will come back.

A new Delphi OE part costs ~$60 including shipping from RockAuto.