adorek24

I replaced both o2 sensors in my 04 Accord 5-manual I-4 with 69000 mi over the weekend because I was getting the dtc p0420, catalyst system below threshold. Good news: that dtc went away. Bad news: the engine light went back on and I pulled a p1157 dtc. This code relates to the primary (upstream) sensor and indicates high voltage in that sensor. Both sensors were Denso OEM, # 234-9040 for the upstream and #234-4797 for the post catalytic sensor. I've reset the MIL using my scan tool and by disconnecting the battery, but in both cases it came back on.

My guess is the pcm is not reading the new sensor within it's parameters. Is the dealership my only option here since they can reflash the computer and have the advanced diagnostics? They are charging $109 just for the diagnostic, so I'd rather not. I've already failed MA emissions and need to get this taken care of. Thanks in advance.

adorek24

turns out my friend didn't secure the electrical connection on the primary sensor and so i snapped it in myself and now the car is fine, check engine light off. glad i decided to double check it before heading to the dealer.