My03evo

iTrader: (1)

So I was looking under my seats for my phone battery I dropped and found a hooked up o2 sensor under my passenger seat still hooked up to looks like the stock mitsu harness. I'm assuming this is the rear sensor since there is no cat and they were too lazy to simply turn it off when they tuned it? It is a LSU 4.2 sensor with 6 wires so I know it's a wideband. The harness goes up into the shifter console but don't feel like ripping everything apart so wondering if this is a normal thing or if someone got to lazy to do it right and turn it off in the tune or something. And I've been getting a PO171 Lean code and wondering if this is why.
Thanks

dastallion951

you prolly have a lean code cuz where that 02 sensor is supposed to go in prolly has an exhaust leak at the 02 bung...

My03evo

iTrader: (1)

Well, the entire exhaust is aftermarket, and part of it is custom made so it's not stock with stock dual bungs and the spot that looks like where it would go there is an o2 sensor in there, assuming that is the precat sensor for closed loop....and there is one right out of the turbo (also have an AEM wideband)

I unplugged it and drove it around and didn't get any CEL's or run any differently, so would that mean it's turned off in the comp? Since I would get an o2 code if it was part of the tune and I unplugged it?

C6C6CH3vo

iTrader: (9)

There might have been a WBo2 sensor in the bung and the NBO2 you see was stashed under the seat melting the carpet

Routybouty

iTrader: (16)

I think it usually takes a couple starts for it to throw the code.

My03evo

iTrader: (1)

I had it plugged in and the engine running, the sensor stayed stone cold. I did not check for power at the connector but most likely it's disconnected somewhere anyway. On my obd2 tool there is no info coming from that sensor, theres only 2 sensors active and they all stay the same if I unplug the harness to this one so it's not even recognized in the ecm so it prob is disconnected somewhere. On my scan tool, the first sensor reads good (one at the turbo), switches good, the second sensor stays around .10-.20 and doesnt go much higher assuming thats because of no cat.

It looks like there's a stock stock sensor at the downpipe right where the turbo discharges, and looks like the wideband is in the precat bung and theres another one in the post cat bung (the one that isnt switching high)