Check engine light

Hi folks
my 98 Infiniti I30 has 111k miles recently I get the Check engine light, I got the Code reader and pulled the code it's p0135, what do I need to do to make it go away. The O2's were replaced at 90k miles before I acquire the car. I am running out of option , what and where is bank 1? I cleared the codes and only to find it on couple of weeks later.
(P0135 Heated O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1))

V6 engine cylinder arrangemen is like the V. First \ 3 cylinders Bank1, next / 3 cylinders: Bank2... Both have their own exhaust manifold, O2 sensor(s)

Points to low voltage, harness/connector problems. Maybe bad O2 sensor? Check http://www.cardomain.com/ride/748507/14
Check charge voltage, att batt AND at ECU.

I've seen new O2 sensors go after only 3 months and 3K miles. Definatly check connections first.