Thread: P0421 Code
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Old 08-27-2010, 11:22 AM   #4
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Join Date: Oct 2007
Location: Edmonton, AB
Posts: 330
Default Re: P0421 Code

Ironically I had P0431 (the same code you got, only for bank 2) go on me about 25 kms after leaving the dealership where I bought it. I promptly returned and asked for some clarification on what they would do. Their garage was packed so I couldn't get in at the moment and couldn't leave the truck for an extended period of time.

The initial response from the Service Agents was that I must have filled the truck while it was running or that I must have left the gas cap off. After I politely told them to eff off because this wasn't my first "rodeo" they gave me some other solutions.

Apparently if the gas is somewhat poor or has been sitting for a while, it can sometimes give the cat issues leading to this code. They also stated that if it had sat for a while, there may be something stuck to the sensor. I then left and cleared the code at home. I added a fuel injector cleaner to my tank and hit the highway for some "spirited" driving.

The code did come back but only for a short while and then went off again. It hasn't been back on for at least two weeks now.


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