For some reason, after removing a silencer that came with my new exhaust, the check engine light came on. After checking it at Autozone, I got the code, P0420, which says that the oxygen sensor for the catalytic converter may have a problem. I have an aftermarket Magnaflow high-flow cat. I checked the price for a Bosch O2 sensor for the converter and it was $86. I said screw it and went home, jacked my car up to see if my O2 sensor was even on. I just had a feeling it MIGHT have came off while I was yanking off the silencer (chances were extremely low), but it was still on. So I"m assuming my O2 sensor really is faulty, and I'm going to have to buy a new one. Is it really about $86 just for an O2 sensor? Also, if my cat O2 sensor went bad, do you think my exhaust manifold O2 sensor will go bad too? Does this have anything to do with my aftermarket catalytic converter?

Thanks a lot guys.

 

It very well may have something to do with your aftermarket cat. If your aftermarket cat flows differently it may throw a code. If the sensor really is bad (check your connections to make sure that they are clean) then yes those sensors are spendy..... If it's the cat giving you the code then find and O2 enumerator, or O2 bypass (google search for it) and install that, then clear the code...

 

Check your gaskets! I got the same code, plus another one that said my o2 sensor was bad, when in fact is was from bad gaskets from my headers. I fixed my gaskets, got the code reset, and it hasnt been on since. Let me know if its the gasket, and i'll explain an easy fix, or look at my OBX header facts, and youll see the red rtv stuff I used. Good luck!

 

I'll check my gaskets. I did reset my ECU just for the hell of it, and the check engine light vanished. Hopefully it'll never come back, but if it does, I'll have to take measures. How can I tell if my gaskets are ruined? Is it as simple as just looking at them seeing if they melted or if they fell off or something? Btw, 19Accord97, when exactly did you get the code? Was it after you installed the WS2 or before? Also, are you still using your factory cat?

 

Most likely it will come back...eventually. It was after I installed both my headers and Apexi WS2 at the same time. Though it was about 8 months after. And yes I am using my stock cat.

I discovered the gaskets were bad, when I changed my oil and actually felt exhaust pouring out where the 2 pieces of the header meet.

An easy way to check is on a colder morning, or after it rains after your car has been sitting overnight, in the morning jack it up, or put it on ramps, or carefully have someone look under the car when you start it so see if the white smoke (exhaust) is coming out.

 

I don't see anything wrong with my gaskets.

I searched for an O2 sensor bypass, but I found this, an O2 Sensor simulator, is that the same?

http://webstore.o2simulator.com/

The thing is, I thought these bypasses and simulators were for the ones who remove the cats, but I didn't remove mine and I still need it? Is it better to get an O2 simulator BEFORE I purchase an entirely new O2 sensor? Or vice versa? Thanks.

 

I think maybe I'll try to get the O2 simulator first, and if the code still comes, then get a new O2 sensor.

 

If you get an O2 simulator and you still get the code (after clearing the code that is) then something is really funky because the O2 simulator bypasses the sensor and tells the car that everything is fine all the time.... I'd test the sensor first if you want to fix the problem right...

 

How do I test the sensor to check if it's malfunctioning and is in need of replacement or not? Because if I can test if it's working, then I won't have to pay $75 to replace my sensor.

 

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