P420 Check Engine Light...

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...

quote:

ORIGINAL: sir_nasty

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.

??

To be totally honest I'm not sure what the exact test procedure is... I believe that the front one on the manifold is the same so you could always "swap" the two, clear the code and see if a new code comes back or the same one comes back, if the same one comes back then it indicates a CAT issue not a sensor issue, if it throws a different code to indicate the primary sensor then you know your sensor is bad...

Okay I replaced my O2 sensor with a Bosch sensor and the lights gone for now after restarting it. I'm hoping it stays gone. I'll post here again if unfortunately the light comes back on.

Okay my check engine light went on again and I got the same P0420 code again. I'm thinking of just leaving the check engine light on, I mean it's only natural that it would go on if I put on something aftermarket on my car. When it comes time to sell the car I"ll think of something then. 

quote:

ORIGINAL: pyaarawala

Okay my check engine light went on again and I got the same P0420 code again.

P0420 points to a bad cat. On a 98-02 accord it's an almost sure thing.

A bad cat? I have an aftermarket Magnaflow cat it can't just go bad can it? Is there a way to tell if my cat is working or not? Because if on a rare occasion my Magnaflow actually did screw up due to manufacturer defects I'll have to ship it out to have it fixed, which will be a pain since my cat's welded onto my headers already.

quote:

ORIGINAL: pyaarawala

A bad cat? I have an aftermarket Magnaflow cat it can't just go bad can it?

Heeeeee

Where's the o2 sensor located on it? At the front or back of the cat?

It's on top, if that's what you're asking. So if I was completely underneath the cat looking up at it, I wouldn't see the hole where the O2 sensor goes.

quote:

ORIGINAL: pyaarawala

It's on top, if that's what you're asking. So if I was completely underneath the cat looking up at it, I wouldn't see the hole where the O2 sensor goes.

Nope front or back is what i was asking. It should be towards the back. If it's at the front the cat was installed backwards and that would be the cause of it coding.

Wow something as stupid as that? I'll have to see again but I do think it might be in the front. Even if it is like 1 cm away from what would be the "middle'" of the cat that would mean that it is in the front? Meaning that it was installed backwards? I guess I would have to go back to the damn place to have it fixed. Does it affect performance in any way?

since it's a high flow cat it's giving you the code because it's reading different than stock, an emulator or simulator O2 sensor will fix that issue.... either that or go back to a stock cat... Leaving the light on isn't a good idea though, because if something else fails you won't know it until it's too late

I looked on eBay and the O2 simulators are generics and cheap. Where can I find a brand named one and which brands are good?

Also, how exactly does it install? The same way as a regular O2 sensor would? Remove it from the main harness and put the sensor into the cat?

try this :
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&rd=1&item=290136816074&ssPageName=STRK:MEWA:IT&ih=019

I don't know good brands off the top of my head and as far as installation I think it normally just connects to the existing wires that run to the o2 sensor, disconnect the sensor and connect the emulator.... was the cat installed backwards?

I don't think so the O2 sensor location is practically in the middle so I can't tell if it's closer to the back or the front. What do you think of that O2 simulator that bougie showed, sir_nasty? Looks good, but it is eBay, and no brand is specified.