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p0420 code help plz

1306 4
2000 Camry LE (I4)
Automatic, 86,000 miles

Exhaust set up: Ripp headers, Magnaflo Hi-Flo cat, 2" or 2.25" piping (can;t remember...)

Ok, so its been about three months since I have had my Ripp Headers on. And no matter what I do, the p0420 code is always coming back to haunt me. Now recently I discovered I have a cali model since replacing the sensor in the front and finding out it is the more expensive one.

So ive replaced both sensors, tried putting an o2 extender on the sensor after the cat. And this code just wont go away. (Catylst Performing Under Threshold). Now that I have figured out that it is a cali model... I have thought it is probably due to me hacking out both cats and putting in one hi-flow cat.

Now any advice at all for getting this code to go away or advising to my questions would be greatly appreciated...

I have thought of the possibility of putting 2 hi-flow cats on the pipe, I have no idea if this would make any difference (make it worse mechanically and/or performance), but since the car came with two, I thought it might help.

Or, is there a way to get rid of the rear sensor without tripping any codes? Or is an o2 simulator my only option?

Thank you all for reading this and hope someone can help! I would hate to put the factory exhaust back on...
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· Premium Member
6,539 Posts
The ECM compares the signal from the front sensor to the signal from the one behind the CAT. If the rear signal is not dampened (or flat) it trips the code. The resistor must dampen out this signal. Give it a try.

· Registered
331 Posts
Discussion Starter · #4 ·
Alright...strange thing happened today. Engine light went off today without resetting it. :) But im sure its not going to be for long...I am interested in doing this resistor set up, seems confusing but Ripp offered that advice too if the o2 extender didnt Ill call them up if the light comes back on to get instructions on how to do it for the cam...unless one of yall kno? Those instructions confuse me, but then again maybe im just thinking too hard into it.

Thanks for the advice!

· I work on euros.
96 Toy Camry Sport
207 Posts
obd2 will turn off the MIL after 40 consecutive trips without seeing the fault reoccur. you must not have gotten it to the place where old cats go to die - fully warm engine, but idling around town=not enough heat to fire off cat. the code stays in history, but the light will stay off.
1 - 5 of 5 Posts
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