Oxygen Sensor Heater Circuit Error

[mci007]

2004 Chevy Tahoe 02 sensor codes 135 and 155, Heater circiut,

LQ9 6.0 Liter and 4L80E trans.

After replacing both front 02 sensors and removing the error codes, drove it for about 50 miles and check engine light came back on, same error codes.

Any thouhgts.

 

[Rivieraracing]

I just replaced my drivers upstream O2 sensor last week due to the 135 code being on, reset the codes and after 100 miles now it's still off!!
I went with AC Delco that I bought off of Ebay brand new for $40, what brand did you go with?