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jweltch
02-04-2008, 12:35 PM
This is on my 01 Durango...

7 or 8 months ago I replaced the cat with a "high flow" Magnaflow cat and both o2 sensors with Mopar parts. It's been fine up until last weekend and now I've got the goddamn p0420 code again.'

How the hell do I figure out which one is the culprit? There are no driveability problems, and it's got just as much power as it's always had (that I can tell). Mileage hasn't dropped either.

BryanRT360
02-04-2008, 12:46 PM
P0420 Catalyst System Efficiency Below Threshold (Bank 1)

I'd say Bank 1 sensor 2

'98R/T
02-04-2008, 02:32 PM
Get an o2 simulator for the second one. I have no cat. and it has not thrown any codes.

mtlcafan79
02-04-2008, 03:20 PM
Most trucks you can tie the sensors to the frame rails without issue. No sims needed.

AmberFireDaK
02-04-2008, 03:48 PM
P0420 (M) 1/1 Catalytic Converter Efficiency Catalyst 1/1 efficiency below required level.


Bank 1 cat 1

Driver side upstream cat........


Did you remove the 2 precats too? or just the main? cause it sounds like your driver side precat is toast

jweltch
02-04-2008, 04:15 PM
Only 1 cat and 1 set of o2's on this one. No precats. All are less than a year old.

AmberFireDaK
02-04-2008, 11:40 PM
Well I don't understand why you would get P0420 then...... if you don't have an cat on bank 1

Bank 1 is the drivers side (odd number cyl) Bank 2 is passenger side (even number cyl)

The code is clearly for driver side upstream cat, which apparently doesn't exist on your truck.... I don't wanna question you but are you sure you don't have precats and 4 02's?

jweltch
02-05-2008, 12:00 AM
The code is clearly for driver side upstream, which apparently doesn't exist on your truck.... I don't wanna question you but are you sure you don't have precats and 4 02's?

Absolutely sure. Been underneath both my 03 Dak (which had 3 cats) and my Durango enough to know the difference! :)

I'll see if I can dig up my old post-cat o2 sensor to plug the hole and ziptie the working one to frame.

AmberFireDaK
02-05-2008, 03:00 AM
Absolutely sure. Been underneath both my 03 Dak (which had 3 cats) and my Durango enough to know the difference! :)

I'll see if I can dig up my old post-cat o2 sensor to plug the hole and ziptie the working one to frame.

I got nothing then man.....that code is sayin' your driver side precat has gone for a shit.

good luck with it :jester:

Hugh Jassole
02-05-2008, 08:41 PM
tie the post cat sensors off to the frame rail and forget about it.

1hotkadota
02-05-2008, 09:05 PM
Stop blowing pot smoke into your intake!:jester:

machine351
02-13-2008, 12:29 PM
you dont have any precat ho2s. so its gonna have to be one of those ho2s before or after cat unless you got an exhaust leak some where. tying into the frame wont do shit. the computer measures the diff between the 2. and adjusts acording.

Duner
02-13-2008, 12:42 PM
My 4.7 set that code about 3 times in the past 8 years. All I did was clear the code each different time it did it and 3 years later it did it again. No big deal. It's a code from a computer. How often does your home computer screw up and need to be re-booted? Same thing here. Just "re-boot" the thing by clearing it and you're probably good to go.

AmberFireDaK
02-13-2008, 03:11 PM
you dont have any precat ho2s. so its gonna have to be one of those ho2s before or after cat unless you got an exhaust leak some where. tying into the frame wont do shit. the computer measures the diff between the 2. and adjusts acording.

No it doesn't..... The upstream 02 helps control A/F....the downstream sensor is only there to ensure the cat is functioning properly. It has no affect on engine management

machine351
02-13-2008, 05:03 PM
No it doesn't..... The upstream 02 helps control A/F....the downstream sensor is only there to ensure the cat is functioning properly. It has no affect on engine management

so I wonder as to why they put 2 ho2s on there instead of just one after the cat? there are reasons as to why the manufacture designed these aspects other than emissions. its for performance to. the 2 ho2s measure the diffrence. why do you think people have to keep reseting the pcm. because it takes time to relearn everything and run all the tests on the systems. it can sometimes take months. trust me man I went to college for automotive tech for two years. I placed third in the state in skills usa. I was taught by two master ase ceritified techs man.

BTLFED R/T
02-13-2008, 05:35 PM
so I wonder as to why they put 2 ho2s on there instead of just one after the cat? there are reasons as to why the manufacture designed these aspects other than emissions. its for performance to. the 2 ho2s measure the diffrence. why do you think people have to keep reseting the pcm. because it takes time to relearn everything and run all the tests on the systems. it can sometimes take months. trust me man I went to college for automotive tech for two years. I placed third in the state in skills usa. I was taught by two master ase ceritified techs man.

But what's a ho2?

slvr03dakrt
02-13-2008, 05:51 PM
ho2's must be some of those super wazzoondous o2 sensors that measure everything.:rockwoot:

mtlcafan79
02-13-2008, 05:51 PM
I belive they are next to the muffler bearings after the O-pipe.

machine351
02-13-2008, 09:08 PM
a ho2s is a heated oxygen sensor. IN the olden days pre 1996 vehicles used a single wire sensor that did not read emissons until after the vehicle completed the warm up cycle. most vehicles on had just one. now they use 2 or more. and they have more than one wire. which means they heat them selves along with heat from the vehicles exhaust. they warm up quicker so they can start controling air fuel mixture quicker. warm up cycle is running air fuel that is preset by the comptuer. then the ho2s takes over along with the computer to find the best ratio for power and emissons.

AmberFireDaK
02-14-2008, 04:01 PM
so I wonder as to why they put 2 ho2s on there instead of just one after the cat? there are reasons as to why the manufacture designed these aspects other than emissions. its for performance to. the 2 ho2s measure the diffrence. why do you think people have to keep reseting the pcm. because it takes time to relearn everything and run all the tests on the systems. it can sometimes take months. trust me man I went to college for automotive tech for two years. I placed third in the state in skills usa. I was taught by two master ase ceritified techs man.

who has two 02's after the cat?? Most vehicles have 2.... 1 before the cat (to help regulate A/F) and 1 after for emissions control.

Alot of newer vehicles are putting 1 sensor on each exhaust bank, then another at a Y pipe or collector.....but they still only have 1 after the cat

I have never seen a vehicle with 2 sensors after the cat...if they exist my apologies. But we are talking about jweltch's truck which we've already established has 2 sensors... Trust me man, the downstream sensor on these trucks has absolutely no bearing on the A/F ratio

jweltch
02-14-2008, 04:16 PM
Here's what my R/T's were equipped with from the factory:

03 Dakota: 3 cats - 1 on each downpipe and 1 after the Y. 4 o2 sensors - 1 before each precat and 1 after each precat. 3rd cat had no sensors.

01 Durango: 1 cat - mounted after the Y. 2 o2 sensors - one before the cat, 1 after.

mtlcafan79
02-14-2008, 05:11 PM
My 02 has six senors of various kinds. Two pre pre-cats, two post pre-cats, one post main cat, and one wideband.

1hotkadota
02-14-2008, 05:17 PM
Damn dude! My 02 has the same setup as Jweltch's 03.

Did you install the wideband yourself?

machine351
02-14-2008, 08:23 PM
who has two 02's after the cat?? Most vehicles have 2.... 1 before the cat (to help regulate A/F) and 1 after for emissions control.

Alot of newer vehicles are putting 1 sensor on each exhaust bank, then another at a Y pipe or collector.....but they still only have 1 after the cat

I have never seen a vehicle with 2 sensors after the cat...if they exist my apologies. But we are talking about jweltch's truck which we've already established has 2 sensors... Trust me man, the downstream sensor on these trucks has absolutely no bearing on the A/F ratio

ya mis understood me man. I know that they have one pre cat and one post cat.

AmberFireDaK
02-15-2008, 01:26 AM
ya mis understood me man. I know that they have one pre cat and one post cat.

so elaborate a bit for me


so I wonder as to why they put 2 ho2s on there instead of just one after the cat? there are reasons as to why the manufacture designed these aspects other than emissions. its for performance to. the 2 ho2s measure the diffrence. why do you think people have to keep reseting the pcm. because it takes time to relearn everything and run all the tests on the systems. it can sometimes take months. trust me man I went to college for automotive tech for two years. I placed third in the state in skills usa. I was taught by two master ase ceritified techs man.

I can guarantee the downstream sensor has no effect on fuel delivery

machine351
02-15-2008, 10:40 AM
up to you man. everyone has there opinon. what nakes you think that it dosent?

AmberFireDaK
02-15-2008, 03:55 PM
I donno....6 years of being on these forums and reading about nothing but these trucks. That an your reason makes no sense