I just installed a high flow downpipe on my 2004 Monte Carlo SS and now im getting a PO420. I was thinking of using an O2 emulator to trick the pcm in thinking the cat is good but to my understanding they wont work on 2004+ vehicles. Is the only way to get rid of this code by sending it in and having the code deleted out of my pcm or is there a better option?

 

P0420 is cat efficiency. If you deleted the cat then that's why its on, or if you put a high flow cat in it, then the pcm may not be liking it. It has to detect a differance in the front and rear o2 sensor readings. If the cat isn't doing a good enough job and the readings are too similar between the 2 02 sensors, it will throw the code. The only way to delete the code is to use a scan tool (autozone may even do it no charge). I've never used an 02 emulator so I don't know if it will keep the light off or not

 

The that they have in AutoZone will only erase your code. Not completely remove it from you r PCM. I know that there are a few members here that have the O2 Emulator and they say it works perfectly.

Check back later on to see if any of them post. Its a holiday weekend so they might not be here as often as they usually are.

 

I just got a ZZP 2.5 downpipe with high flow cat installed 2 days ago. My rear O2 senor was bad so yesterday I had them install a new one (they had to order it). So far so good without throwing any codes. I drove the car approx 10 highway miles. Do you think you might have a bad O2 sensor? My car has 62500 miles on it so I'm not sure when they go bad, if it's by age or mileage.

 

I thought he just wanted the light out, lol, I didn't know u could completely remove a code

 

The code will come back.


Amy, it may not show with that few of miles. It's my understanding it takes three start cycles (tests) before it trips the CEL.

 

Well, I'll keep my fingers crossed!

 

The O2 sensor is working perfectly. I know its because of the cat because i got the light after i installed the downpipe. Remember mine is a 2004 so take a look at this link... http://www.3800performance.com/Merch...oduct_Count=17

 

Has anybody tried the non fouler mod? It's supposed to create more distance between the O2 sensor and the exhaust gas that's either been through a high flow cat or none at all. The resulting difference should supposedly take out the codes.

Non Fouler Link

 

Well, I thought my O2 sensor was OK before too, but after they took it off the car it looked all burnt and stuff, so I got a new one installed. It's been a week and still no code has been thrown.