First time poster, long time reader here. Could use a little help.

I did a 100k tune up on my '05 cooper s a few months back, which included replacing the thermostat. When i removed the housing to get to the thermostat i noticed it was keyed (to ensure proper alignment?) to the seal, however the new thermostat was not, and so didn't fit properly in the seal (it came with it's own, which covered only the thermo, but i didn't think i could use it due to the stock one being made to fit the length of the housing) so i had to "modify" the original to fit the new thermo (in hindsight, probably not the best idea)

long story short (too late?) since then me SES light's been on and gives me the P0128 code (coolant temp below thermostat regulating temp). I'm guessing it's related to my earlier poor judgment and any suggestions that would let me keep the aftermarket thermo (although I will gladly purchase a new OEM one if necessary) would be appreciated.

 

Did you install a lower temp, such as 180 deg, thermostat?
If so, what part of the country do you live, such as a colder area?

 

It's a Failsafe marked with "OE recommended temperature". And i'm in southeast PA, but this was over the summer.