Question

2011 GMC Sierra 3500 Duramax with engine code P205B, what is the reductant tank?

Answer 1

Reductant tank is the same as DEF (Diesel exhaust fluid) which reduces the NOx in the exhaust so reductant tank is the def tank.

 

you can reset the code first and see if it comes back, dealer recommends reflash with the latest updates if the code comes back and/or  replace tank/pump  assembly 

Answer 2

P205B Chevrolet Code - Reductant Tank Temperature Sensor Circuit Range/Performance
Read more: https://www.autocodes.com/p205b_chevrolet.html