I have a 2001 Tundra with 90,000 miles. the "check engine" light came on a couple of days ago, so I hooked up my innova computer tester to it. The reader came back with PO 155 - 02 heater circuit, bank 2, sensor 1. I guess this tells me that the sensor is heated, but which location is which in? Is it left to right as you are sitting in the truck? And I guess sensor 1 is in front? Should I change both front ones at the same time? The truck was bought new by me, so I know the history. I had taken the truck in (in 2002) for the recall and had all 4 sensors replaced then.

Bank 2, Sensor 1 = Passenger Side, Front Fuel/Air Sensor

Solution: Replace

DIY Tip: Buy two and replace both sides at the same time. The other side will trip in a short while anyway.