My check engine light just came back on after having the new manifold and right side O2 sensor installed. I pulled into a nearby AutoZone and they pulled the code for me. They said it was PO 135. They said that it was the right side O2 sensor. Later in the day I took the truck back to the dealer. They pulled the code and told me it was the left side O2 sensor. Anyone know who's right? I don't have the FSM yet so I can't look it up.