I have a pre-owned 2005 Trailblazer which I was told by one mechanic needed a new thermostat. They were gonna charge me $333 for the whole job. The check engine code PO128 comes on and off now for the past month.
Another mechanic said they tested the temps and couldn't justify replacing the t-stat but replaced some wiring that was supposedly sending the wrong signal? Cost me $200 now I'm getting the code again but interestingly it only seems to be coinciding when I use my heated seats...
The temp guage stays steady in the middle, no probs with cool or heat. Can the heated seats wiring be sending a signal that turns that code on or do I need a new t-stat? Something else entirely?

I appreciate your time and help!

Thanks,
Katie