02AccordLX

So I received an 02 Accord LX from my mother-in-law and knew it was going to need some work but I did not know what I would be in store for. So I could hear the exhaust had a leak but there was no CEL so I figured it was after the catalytic converter and secondary oxygen sensor and would be an easy fix. I get the car in the air and theres NO cat, NO o2 sensor and the genius "mechanic" who did it cut the o2 sensor plug off the car side and simply left the wires hanging and welded in a piece of pipe in place of the catalytic converter. This is where I am confused because there is NO CEL and yes the bulb works. It illuminates when you start the car and then stays off. When I first received the car it was doing the 10 flashes of the CEL and Maintenance light indicating the oil life counter wasn't reset in 7500 miles or something, which clearly shows both lights in the dash are working. I have since reset it and now it goes off as it should. So how is this possible!!!?? my mother in law purchased the car 2 years ago and bought it this way so I have no idea of finding out what was done. I am thinking someone did some sort of bypass but I cannot find ANYTHING matching this situation out there on the interweb. Please, I need help. I would like to replace the exhaust and reintroduce a catalytic converter and rewire the o2 sensor.

SO, how is it possible for the car NOT to throw a CEL with NO secondary o2 sensor and NO cat!? The only bypasses I find involve wrapping foil around the plug and leaving it zip tied to something (or some nonsense like that) and the second involves resistors in plugs which neither options are in play here.

99stockcivic

Even though the light doesn't come on, I suspect if you check the codes on the car, it will show something . I had a car that after awhile the Check Engine light would just turn off but left the trouble codes in the computer.

In any case, sounds like you need to drop in a new exhaust from the cat back and get some O2 sensors to solder back onto the wiring.

02AccordLX

Thanks for the input. I guess to validate this theory I'll have to check for codes. If this is the case, is there a wire diagram for the car side for the secondary o2? Not sure if I should source another female plug so the o2 is straight plug and play, or if I should get a universal and wire it directly to the wires hanging from the car?

Not saying you're wrong but its just so hard for me to fathom someone essentially cutting the o2 sensor wires and then the cel eventually going away on its own. I've never heard of this but I wouldn't be surprised.

99stockcivic

I understand. I mean it is possible to fool the sensors, it usually involves putting in a mechanical bypass. Read here: https://www.s2ki.com/forums/s2000-un...ulator-229959/

If that's what you want to do, then that's how I believe it's working right now.

If presuming you want a less stinky and more emission compliant vehicle, but that's just me presuming you need to pass an inspection, in which case you need to swap all that out for a cat and sensors. If you have the time to make it look nice, I would try and build a connector, but if you are in a "I don't care" mood, then wiring it is fine, it's going to last 100,000 miles or more so it's not something you will be swapping for a long time anyway.

02AccordLX

Yes, I have seen that as a solution but that is not the case here. That link is showing an o2 sensor in a de-fouler just to move it further from direct exhaust flow and helps eliminate a cel. On this car, there's no o2 sensor at all. Its gone, wires cut and a piece of pipe welded in place of the cat. I definitely want it right and im going to install an entire new exhaust from the manifold back, including a cat and o2 sensor. I'm just trying to figure out exactly how this setup is working as it is now. I've read on some post I can no longer find that someone used hondata to actually turn off the secondary o2 sensor and since the ecu is no longer looking for it, it won't throw a code. But I highly doubt that would be the case here. I've yet to confirm the ghost code theory but I guess I'm just going to install, cross my fingers and hope doing the right thing doesn't now throw a cel lol

again, if anyone can provide some sort of wire diagram for the car side of the secondary o2 that would be excellent. I'm just going to buy an o2 with a pigtail and solder/shrink tube the connections. If done clean and correct it could very well outlast a plug exposed to the elements.