Which sensor is throwing these codes?
 

My parents truck is throwing codes p2a01 and p0137. They both say sensor 1/2. I read bank 1 sensor 2. When I ordered the sensor they say that both are the same. Which sensor is is the one I should be changing out?

More details on the truck? What year?

Wow forgot all about this one. Well i changed the rear sensor and all has been good till a few weeks ago the p2a01 came back on. I cleared it but it takes a couple days for it to come back, any suggestions? Its an 09 ram 6.7 i believe

Anyone confirm if the front and rear o2's are interchangeable? The dealer said they show up as the same number but sometimes the difference is the length of the wires