My 98 Dodge Stratus 2.4 four cyl with 38k miles set a code PO171 which my OB2 Tool said was Bank 1 O2 lean. I reset the computer to find out the the code came back days later. Next I replaced the upstream (before cat) o2 Sensor. I just need to make sure I replaced the correct sensor. Usally bank one means the bank of CYl with #1 piston. In this case is bank 1 the upstream or downstream sensor since the car only has these two. Did I replace the correct sensor or could it be something else causing this code. I know the senor can be good and the lean condition can be something else but wouldn't the downstream sensor be lean too them? Anyone else experience this?
Thank you for your time.
Sal