Blazer Forum - Chevy Blazer Forums - 02 sensor and thermostat code problem

I have a 2004 4dr 4x4 blazer with the 4.3 V6 engine. My Service Engine Soon light came on and so I went to Autozone and ran the codes. It came up with the P0155, Bank 2 Sensor 1 Oxygen Sensor. I replaced it. Light stayed on. I ran the codes again, came up with a P0155 and P0128. So I replace the Thermostat (the temperature of the Vehicle was running low, would not get anywhere close to 195 degrees so it needed it.) Light stayed on. I ran the codes for a third time. Same thing, P0155 and P0128. The Vehicle is running about 195 degrees so I am assuming that the thermostat is fixed and has plenty of coolant. I unhooked the battery to see if that would reset the code and it did not work. The oxygen sensor fuse is good. I am running out of solutions. Anyone got any ideas?????