02 chevy blazer, P0155 error code

[tjmjr72]

I have a 2003 chevy blazer 4x4 4.3lt v6, I am getting error code P0155, does it meen the RT bank upstream o2 sensore is not working, and is that the one between the rt exaust manifold and the cat?
Thanks

[dewaynep]

That code means the heater is not working on that O2 sensor. It could be a wiring issue or a bad heater in the O2 sensor. That should be the first sensor on the right bank (right from drivers perspective).