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All right i really want this code to stop showing up P0420 1/1 Catalyst Efficiency Low. So if i buy a magnaflow high flow cat with an 02 bung in it and have it welded in place of the existing cat will it fix the problem?

For the 02 sensors as far as i see there are 2, one in the cat, and one right before that, is that correct. Thanks for the help

You shouldn't have to buy anything non OEM to fix the problem. I haven't had this issue before, but there is definately an OEM fix. That is unless you were just looking for an opportunity to put an aftermarket cat in. If so, and you have the spare funds, then do it and best of luck I would imagine that there is a decent chance that it fixes the problem. Make sure you are looking at it from all angles. If you put an aftermarket cat in, what else will you be affecting?

well if i just buy OEM will the stock cat for an RT the same as the base neons for 00-02?

I am not certain, but I would imagine not because the R/T neons have a different exhaust setup.

Have you replaced the first o2 sensor? as far as the flow characteristics go i believe base and r/t cats flow the same.
according to Mitchell , the se,es are the same and the r/t is different.
converter #'s
5278622AC = R/T
5278345AE = es,se
if you haven't replace the sensor i would start there.
good luck.
BRR has more access to factory #'s than i do.
hopfully he will chime in.

where is a good place to buy the 02 sensors, and whats going to be the cost for them?

I would campare price between NAPA and the dealer.
average is $60.00 . some are more - some are less

i have that same problem. I didn't pass CA smog test. And will have to replace cat/ o2 sensors..... then i was thinking I'm going to replace my whole exhaust system. I got a 3 month permit until i pass the smog test.

if possable go back with an OEM cat. Ive seen far too many am cats fail at 50k miles. Plus there are little to no performance gains going with a hiflow. All cats are hiflow now. That became big on older cars when we first started doin emissions stuff. Those cats blew almost as bad as my ex gf.

to fix my 420 code I first replaced the senor on the cat. I couldn't find that senor at store due to the fact that it has to fit in a small area and the ones at autozone and advance were too long.

I picked one up at the dealer 138.00

It didn't fix the problem. I replaced the cat with a mangaflow from Modern. The one with the o2 sensor built into it. It did fix the problem.

Only issue I had was the hi flow cat I bought was shorter then stock and it need to have extention pipe weilded to it.

I just passed Maryland Emissions with it no problems. I've about 48,000 miles on the cat so far no issues and I drive at least 100miles per day

As for performance gains I don't know but with it a UDP a CAI and keeping it 70 and under I maintain about 38 miles to the gallon on 87 oct gas.

My car has about 130k on the engine.
Its a 01 SE ATX

Ok i just put in both new 02 sensors, and still the code. So i have to go around and buy a new cat. Where would i find one that is made and fit the R/T. I looked on dodgeparts, and it is <500 dollars for the cat. Is there anywhere i can find one for cheaper? Thank you

you did clear the codes after you replaced sensors? or did you just replace sensors?

yeah disconnect your battery for 10-15 mins then reconnect the battery and see if it goes away.

Yup i had the car disconnected while i was installing, then i plug in an it was alright for a little bit. Then after a couple miles of driving i got the code up again.

Don't just rely on codes for your diagnonsense. That code could be caused by other things besides a bad cat or O2 sensors. What kind of fuel mileage are you getting? If this is your 2nd cat that's going bad, something else is wrong.

If you cant figure it out, take it to the dealership and have them look it over. Its what I do if I have a problem. (Which I never do )

This is the original cat on the car as far as i can tell, and the car has 105K miles on it. I am getting 24-26 mpg and i mostly drive on the highway at 70 mph. So i dont know if that is good or bad for an RT but by looking at other models, its pretty bad. Any ideas?

get a new cat.. sounds like its getting plugged up... you could get one of the replacement cats from modernperformance.... or you could get a high flow cat, and have someone make you a downpipe to put the cat in the middle of.. whatever is cheapest i guess...

dansou5 wrote:This is the original cat on the car as far as i can tell, and the car has 105K miles on it. I am getting 24-26 mpg and i mostly drive on the highway at 70 mph. So i dont know if that is good or bad for an RT but by looking at other models, its pretty bad. Any ideas?

i get that mpg in town. i would try and find a direct bolt in, easy , may cost a little more but , thats the route i would go.