code 0420

[jct61765]

Autozone is telling me i need a new cat. The check engine can be shut off and will stay off for like a week or more. then all of a sudden it comes on. Does anyone know if that all it is?

[xrturbo]

i am pretty sure that is the code of death, the most expensive code that can pop up.

[MDW25gt]

i am pretty sure that is the code of death, the most expensive code that can pop up.

 

yeah right!

[porcupine73]

Hi jct61765. Yikes that does sound like an expensive code! But seriously, maybe you just have an exhaust leak or something? I don't know but would maybe just replacing the rear o2 sensor would fix it, I mean how does autozone know the rear cat is bad without inspecting it?

[johnceggleston]

do a search here for o2 sensors or p0420, lots of talk about them. the only area of disagreement seems to be on wether you rplace the front o2 sensor or the rear. in my 97 obw i replaced the rear , and TAADAA, no more CEL no more p0420. i replaced the rear with a used sensor i had on hand, it didn't cost me any thing to try. also check onl;ine prices for replacement parts prices.

 

Hi jct61765. Yikes that does sound like an expensive code! But seriously, maybe you just have an exhaust leak or something? I don't know but would maybe just replacing the rear o2 sensor would fix it, I mean how does autozone know the rear cat is bad without inspecting it?

[jct61765]

Hi jct61765. Yikes that does sound like an expensive code! But seriously, maybe you just have an exhaust leak or something? I don't know but would maybe just replacing the rear o2 sensor would fix it, I mean how does autozone know the rear cat is bad without inspecting it?

Thats what I figured too. I'm more into Toyotas.

[xoomer]

(takes of RED autozone shirt) Most likely the Autozoner just went out and read it off the code reader, without verifying it with the computer inside which makes suggestions into what your problem could be, here in Seattle, I will call the dealership if some code comes up I can't fix And Ask for suggestions..

[nipper]

Never trust a counter person to tell you what you need.

 

You need to replace the 02 sensor. Its rare that a sooby needs a cat. Also even if it does need one, the 02 sensor still needs to be replaced, so replace the cheapest thing first.

 

The first sensor shold be a sooby sesnor and that communicates with the computer, The second can be generic and that one is for cat performance.

 

Last month i got this code, replaced the front 02 sensor, no more problem (of course it happened 2 days before inspection).

 

Never rely on an autoparts chain store person to diagnose your car.

 

nipper

[jct61765]

thanks for the information.

[xoomer]

Never trust a counter person to tell you what you need.

 

nipper

 

I'm a counterperson and I'm good at telling people what they need..

 

If you go to autozone, Try and get a senior Autozoner, They tend to have a High turnover rate and most stores have at least one or two experianced persons working... Like I'm the only red shirt that knows what I'm talking about in 2 stores, because I shift between The Burien and Seattle store.

[nipper]

I'm a counterperson and I'm good at telling people what they need..

 

If you go to autozone, Try and get a senior Autozoner, They tend to have a High turnover rate and most stores have at least one or two experianced persons working... Like I'm the only red shirt that knows what I'm talking about in 2 stores, because I shift between The Burien and Seattle store.

hehe ok i apolgize most the counter people i run into have no automotive expierience at all and just read the codes as they sit. i heard one say to somone he had 4 codes and needed 4 very expensive sensors. i sort of shook my head as i didnt want to get involved diagnosing, i just told him to get a second opinion.

i also applied at a chain as a manager ( i was between jobs) and told i was over qualified (automotive engineering degree, many years pulling wrenches etc). . Oddly i like working retail.

 

And as you said there is high turnover, how is someone off the street supposed to know that the person hes talking to knows what he is talking about?

 

 

 

nipper

[Olnick]

I'm a counterperson and I'm good at telling people what they need..

 

Ah, but xoomer--you've already proven your intelligence. Tou drive a Subie and you frequent this board!

 

(And I'm not being flip. I mean that sincerely.)

[rallyruss]

all three of the most common probelms have been mentioned in this thread.

 

if you dont know how to propery diagnose then you will end up "shotguning" parts at it untill its fixed. That can get rather costly.

 

A code P0420 is quite often a bad cat. the cat monitor is rather acurate.

 

It can also be triggered by strange driving conditions, one of the o2 sensors failing (usually the rear) or an exhaust leak.

 

In california the emissions waranty has to covers parts like the cat for 100K miles or 10 years. I dont know if other states are the same.

 

If the cat did fail It would be wise to determine why. does the car have a fuel/spark issue? or was the cat just damaged by a rock in the road?

 

I too have worked as a parts counterman in the past and I would like to think I helped a lot of customers fix cars. But I would trust an actual mechanic who knows how to diagnose a little bit better.

[nipper]

all three of the most common probelms have been mentioned in this thread.

 

if you dont know how to propery diagnose then you will end up "shotguning" parts at it untill its fixed. That can get rather costly.

 

A code P0420 is quite often a bad cat. the cat monitor is rather acurate.

 

It can also be triggered by strange driving conditions, one of the o2 sensors failing (usually the rear) or an exhaust leak.

 

In california the emissions waranty has to covers parts like the cat for 100K miles or 10 years. I dont know if other states are the same.

 

If the cat did fail It would be wise to determine why. does the car have a fuel/spark issue? or was the cat just damaged by a rock in the road?

biggest reason for failure is bad gas or running too rich.

 

i think about 10 states now use california emissions, mostly in the northeast. The good thing about it is that its becoming less and comon to replace a cat.

[xoomer]

 

And as you said there is high turnover, how is someone off the street supposed to know that the person hes talking to knows what he is talking about?

 

 

 

nipper

 

The permastained hands, and the grease under our nails, oh wait when you own a subaru, thats normal

[jct61765]

all three of the most common probelms have been mentioned in this thread.

 

if you dont know how to propery diagnose then you will end up "shotguning" parts at it untill its fixed. That can get rather costly.

 

A code P0420 is quite often a bad cat. the cat monitor is rather acurate.

 

It can also be triggered by strange driving conditions, one of the o2 sensors failing (usually the rear) or an exhaust leak.

 

In california the emissions waranty has to covers parts like the cat for 100K miles or 10 years. I dont know if other states are the same.

 

If the cat did fail It would be wise to determine why. does the car have a fuel/spark issue? or was the cat just damaged by a rock in the road?

 

I too have worked as a parts counterman in the past and I would like to think I helped a lot of customers fix cars. But I would trust an actual mechanic who knows how to diagnose a little bit better.

Other than the code it runs great. I can shut it off, but it does come on after a while. Last time was about 2 weeks. I'll try the rear o2 first.

[xrturbo]

i replaced a cat in a used 97 ob at work last week and a customers 98 GT, one broke up, the other went into meltdown.

[nipper]

i replaced a cat in a used 97 ob at work last week and a customers 98 GT, one broke up, the other went into meltdown.

 

i remeber back i the 1980's and 1990's where cats were being replaced quite regularly. Back then thy onlyu had to last 60,000 miles. They have come a long way.

 

nipper

[Soutthpaw]

Autozone is telling me i need a new cat. The check engine can be shut off and will stay off for like a week or more. then all of a sudden it comes on. Does anyone know if that all it is?

Remember these guys work at autozone for near minimum wage because they are not smart enought to actually be able to fix the vehicles else they would be working in a shop for a whole lot more money!!!

 

I tell all my customers that just because a DTC says something is bad, it does not mean it is bad. there are multiple causes that will trigger DTC's... Without going through the complete diagnostic flow chart for that code you are often just wasting money replacing good parts with good parts

 

Code will often reset after a series of "good" starts after the code is triggered. so if you drive the vehicle 3 times for example and the code does not reoccur then the light resets (code will be stored in memory though).

DJ