Error Code P0420
Senior User
Joined: Nov 2006
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sure, switch bank 1 and bank 2 post cat sensors, see if the code follows the cat or the sensor. its not a lot of work, but if you cant use a ford scan tool its about the only thing left. youre gonna have to clear the code and see how it comes back, disconnect the battery or have autozone clear it. not to knock on the autozone or advance or checker guys or anything, but they dont get the same traning a technician does, ask the experts.
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Senior User
Joined: Oct 2005
Posts: 328
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From: Indianapolis, IN
My "expert" is out turkey hunting right now 
That's main reason why I asked here, I knew I would get the help I needed by people here. So take the sensor after the cat on both sides out and switch them, reset the code, and if it switches to bank 2 then it's the sensor. If it stays bank 1 it'll be the cat. Is that correct?
That's main reason why I asked here, I knew I would get the help I needed by people here. So take the sensor after the cat on both sides out and switch them, reset the code, and if it switches to bank 2 then it's the sensor. If it stays bank 1 it'll be the cat. Is that correct?
Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
99.9% of the parts people at AZ are idiots. The only training they have is how to sell you a part even if you don't need it. I'm surprised they didn't try to sell you a set of four O2 sensors to fix your cat.
You either need a cat or you have an exhaust leak upstream of it that is sucking air in. O2 sensors don't cause this code.
The only way to test the cat is to compare the reading of the up and downstream O2 sensors with a multi channel lab scope, graphing multimeter, or scanner.
You either need a cat or you have an exhaust leak upstream of it that is sucking air in. O2 sensors don't cause this code.
The only way to test the cat is to compare the reading of the up and downstream O2 sensors with a multi channel lab scope, graphing multimeter, or scanner.
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Senior User
Joined: Oct 2005
Posts: 328
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From: Indianapolis, IN
I forgot to ask this earlier, which side is Bank 1? Also how would I know what cat I need? I've found some that are oval, round, and oval w/ air tube. Might as well go ahead and start pricing them out just in case. My pipes are 2 1/5"
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Senior User
Joined: Oct 2005
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From: Indianapolis, IN
Alright, thank you. As long as the weather is nice after work today I'm going to switch the O2 sensors to see if it kicks the error code to bank 2 or if it stays at bank 1.
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Joined: May 2003
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From: E.Lincoln County, NC
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From: E.Lincoln County, NC
P.E. sells these for Mustang owners that installed the off road pipes, eliminating the cats ........ technically for off-road applications ...... I put 60K+ miles on my Interceptor after installing the MIL's with no problems ....... 60K off-road miles ..........
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Joined: Nov 2006
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if your catalyst has low efficiency it could plug up and cause your truck to run like total crap at any moment. if it was sucking in air you would have a lean code, which you dont. its either the cat or the sensor. dont let yourself get side tracked here. The governement says that auto makers have to warranty cats up to 80000 miles. but not the labor, beyond that its your mess. Or you could just keep driving it, the only reason the check engine light is on is beacuase you are potentially polluting with a failing cat, half of the requirements of OBD 2 are emissions related, and like 90% of all Powertrain DTC's are emissions related too. its a long story, but in short get a new cat or get a new sensor. as long as the bolts arent completely rusted you should be able to get them off with air tools, maybe hand tools. if they are super rusty=torch.
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Senior User
Joined: Oct 2005
Posts: 328
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From: Indianapolis, IN
Yeah mine has 98,000 on it. I'm a little over the 80,000 mile point. Weather was chilly last night so I wasn't able to get out there and switch the O2 sensors around, so I'll try that this weekend, it's supposed to be nice.
