Help! P0420 code
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Instructor
Joined: Sep 2019
Posts: 226
Likes: 18
Help! P0420 code
I have an 02 z06, with 36k miles. I was driving today for about 20 minutes in the city and my CEL came on! I checked and it’s the P0420 code. I installed a vararam intake about 200 miles ago, and also a b&b bullet axle back exhaust about a week ago. Would either of these be the case ? How do I fix it, a tune? I’ve read that a lot of people who get this means a cat is going out, but my car has only 36k miles so I don’t think it’s that. Thanks
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,434
Likes: 3,981
From: Cape Coral, Florida
Without a scan tool to look at the front and rear O2 sensor waveforms you would only be guessing !!...you can however look for any exhaust leaks aft of the front O2 sensor to just forward of the rear one !!...some good videos below !!
Melting Slicks
Joined: Feb 2001
Posts: 2,800
Likes: 356
From: Northville, MI
Get a can of CATCLEANER and when you have only 4 gallons left in the tank, add the contents, drive about 20 miles and then fill up with gas. When your home, delete all the codes and then restart the car. Did it on our Buick when it the code caused the service engine lite to stay on. It lasted about 3 months and came back on. Repeated the procedure and lasted another 2 months till we sold it. It was a $50 fix instead of a $1500 repair. Told the new owner what I did and he also felt it was good for him to do.
Melting Slicks
Joined: Mar 2018
Posts: 2,502
Likes: 187
From: California
Who did your exhaust / intake? Loose connection you can reach down and reconnect the o2 sensors on the manifolds. Try resetting the dtc codes then pull the battery right away. Insert key use up and remaining charge. Replace after 15 -30 mins. It’s a possibility the car needs to be retuned for the vara with the exhaust I’m not sure! but I do have a stock modified file when my vararam system on if you have a hpt to flash it.
