I installed new thermostats last weekend as a part of other work. Mine now does the same as yours. Old one(s) was defective, even threw a code once in a while. Truck now indicates 205 on the instrument cluster all the time, running empty. Haven't towed yet. It used to run much lower.
2005 GMC Sierra 6.6 WT 2WD. 540k miles
Last edited by pj951; 08-11-2019 at 11:27 PM.