02 Dodge Intrepid check engine light is on. P0138 oxygen high voltage Bank 1 Sensor 2 the auto part store said. They suggested cleaning it? The mechanic said i have 14 miles of wire...I am lost & can"t spend a fortune to figure it out. Sorry I am not sure where to even post on here.

 

The mechanic reset it & it stayed off for about 30 miles before the check engine light came back on. When the auto part store ran the test the light went off again for about 20 miles, then came back on.