o2 Sensor issues

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Madcrafter52
Posts: 4
Joined: Sat Dec 24, 2022 3:42 pm
Location: Langley, BC

o2 Sensor issues

Postby Madcrafter52 » Sat Dec 24, 2022 3:51 pm

Having some issues with a rough idle and rpm surging under load on my 1997 Pathfinder (auto, 4x4) I scanned my codes and they all point towards o2 sensor 2 bank 2. However when I watch the live data both o2 sensors on bank 2 are giving some weird data. Sensor one is stuck at 0V no matter what and sensor 2 is suck at 2.90 (the engine is fully warmed up) also my MPG's are really bad. So do I just have 2 bad 02 sensors or is something else at play? Thanks for any help :D
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VStar650CL
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Joined: Wed Dec 09, 2020 6:19 pm

Re: o2 Sensor issues

Postby VStar650CL » Sat Dec 24, 2022 4:30 pm

The ECM doesn't really use the rear HO2S's for running the engine, they're only there to monitor the cats. So it's possible the rear sensor has been going bad for awhile but went unnoticed till the front one failed, which is used for running the engine. I just checked the WD's and power/ground are common for all 4 sensors, and the data wires run straight to the ECM without intervening connections. That makes a wiring issue doubtful. I'd check power and ground anyway, but if they show up good then it looks like two bad sensors. See info starting on EC-133:
https://www.nicoclub.com/service-manual ... 7%2Fec.pdf

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Madcrafter52
Posts: 4
Joined: Sat Dec 24, 2022 3:42 pm
Location: Langley, BC

Re: o2 Sensor issues

Postby Madcrafter52 » Mon Jan 02, 2023 7:39 pm

Just replaced both o2 sensors and now she runs like a top, hopefully my MPG will improve as well!


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