Author Topic: p0420  (Read 712 times)

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bigdman84

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p0420
« on: Mar 12, 2015, 05:48 PM »
What can  cause this code mind you before  I replace the cat the light came on then I replaced the cat with a universal cat and replace the rear o2 sensor with a o2 bung and  spark plugs that worked for a long bit now the codes on  never replace the bank 1 o2 Sensor could that be y the light is on any thoughts

Offline Tom Creg

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Re: p0420
« Reply #1 on: Mar 17, 2015, 06:44 AM »
Unfortunately, in my experience a universal cat was what set my P0420 code. Basically, the universal was just different enough from what the car wanted so it would set the code. That was on an 02 Grand Prix SE with the 3100. I had a universal cat put in because my stock cat was plugged and it ended up throwing that code all the time. I found if I kept that code deleted I would maintain my fuel mileage for the most part. So if you have a way of tuning that code out or at least telling the computer that the cat in the car is just fine, it should keep that code off. Or you can go and have a direct fit cat welded in place of the universal one. Just my opinion though from my past experience. I could be wrong, only owned an LS4 for about a month now

bigdman84

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Re: p0420
« Reply #2 on: Jun 07, 2015, 08:10 PM »
How can u delete a p0420 code I try ed on a scanner it wouldn't delete it I had to take off my beg battery terminal to clear it but if I drove a few miles it comes back and stays on what does that mean is it bad or the computer doesn't like the cat? What about my o2 sensor before the cat I never change that I change the rear one but I have a o2 bung on it as well could that be my issue sorry for the few month response I'm tired of this car posting problem after problem. Any thoughts thanks

Offline tomtom123

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Re: p0420
« Reply #3 on: Jun 14, 2015, 06:36 PM »
Well, you can get the code tuned out but it probably won't really help any issues except the car might think everything is fine. Maybe you can take it to a mechanic and have them run live scans of the sensors to see if your 02 sensors are reading correctly. That's probably what I'd try first to rule out the sensors. If the sensors are good then it's probably the cat thats causing the problem.