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P0420 with aftermarket cat

 
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rpm1200
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PostPosted: Sat Jun 11, 2011 12:38 pm    Post subject:  P0420 with aftermarket cat Reply with quote

Hi all,
I have a 2003 Impala with the 3.4. I got my cat and O2 sensors replaced at an independent shop last September but my MIL/CEL started coming on within a few months of the repair. I'm sure it was a generic replacement and not OEM. For a while the MIL was going on and off every few weeks but since March or so it's been on constantly. I just got the codes read and the only fault code is P0420. Anyway, is there someone located near me (Rochester, NY) who could tweak the PCM to ignore the P0420 code due to the aftermarket cat? I need to be able to pass inspection later this year and in New York State an MIL is an instant inspection fail.
My apologies if this is the wrong forum.
Thanks, rpm1200
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Pitch Black SS
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PostPosted: Sat Jun 11, 2011 2:56 pm    Post subject:   Reply with quote

Welcome to the site!!!

It could be either the cat or the sensor. These cars dont like Bosch sensors and it seems that most shops use them (probably because they are cheaper)
however, it is more than likely the cat like you suspect.

Option 1 - You need to find a shop with tuning capabilities to delete the code from the PCM. Not sure what they will charge.

Option 2 - Find local member with a HPT to do it for you. Prob cost you a couple beers / lunch

Option 3 - What I did, bought an off the shelf PCM from a vendor with the code deleted. You also get the benefit of the other changes included in the tune. Cost is roughly $100 + core charge

Option 4 - O2 Simulator, if you can find one, they are hard to find since the EPA cracked down on the manufacturers.

Option 5 - Anti Fouler Mod, using an anti fouler, you can space the O2 sensor further out of the pipe. It doesnt always work, but costs just a few $$ and 15 min of your time.

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DennisW
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PostPosted: Sun Jun 12, 2011 3:21 pm    Post subject:   Reply with quote

Pitch Black SS wrote:
Welcome to the site!!!

It could be either the cat or the sensor. These cars dont like Bosch sensors and it seems that most shops use them (probably because they are cheaper)
however, it is more than likely the cat like you suspect.

Option 1 - You need to find a shop with tuning capabilities to delete the code from the PCM. Not sure what they will charge.

Option 2 - Find local member with a HPT to do it for you. Prob cost you a couple beers / lunch

Option 3 - What I did, bought an off the shelf PCM from a vendor with the code deleted. You also get the benefit of the other changes included in the tune. Cost is roughly $100 + core charge

Option 4 - O2 Simulator, if you can find one, they are hard to find since the EPA cracked down on the manufacturers.

Option 5 - Anti Fouler Mod, using an anti fouler, you can space the O2 sensor further out of the pipe. It doesnt always work, but costs just a few $$ and 15 min of your time.


Or, Option #6 - Replace the cat with an OEM replacement one instead of a cheap "universal" brand. One thing for sure is these cars definitely do not like the cheap cats. I'm not sure I agree with you about the Bosch sensors, put both front and rear Bosh units in my '04 3.8 almost a year and close to 34k miles ago and they're working just fine, along with the Maremount OEM replacement Cat. Cost of the converter from Rock Auto was like $225 and the Bosch sensors ran me something like $80 for both.
I know some very knowledgable people on here like BB Engineer say only use the Delco converters but I gotta believe a properly engineered and manufactured OEM replacement converter will and should work properly.

Just one man's opinions and experience.....you mileage may vary
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Pitch Black SS
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PostPosted: Sun Jun 12, 2011 4:18 pm    Post subject:   Reply with quote

Just going with the hundreds of w-body owners that have tried Bosch sensors only to have issues. Same things with spark plugs.

Will Bosch sensors work? Possibly, but after 10+ years of dealing specifically with W-Bodies, I can count on 1 hand the amount of successful Bosch O2 sensor installs.

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DennisW
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PostPosted: Sun Jun 12, 2011 8:13 pm    Post subject:   Reply with quote

Pitch Black SS wrote:
Just going with the hundreds of w-body owners that have tried Bosch sensors only to have issues. Same things with spark plugs.

Will Bosch sensors work? Possibly, but after 10+ years of dealing specifically with W-Bodies, I can count on 1 hand the amount of successful Bosch O2 sensor installs.


well, feel free to add me to one of those fingers
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PostPosted: Sun Jun 12, 2011 11:26 pm    Post subject:   Reply with quote

DennisW wrote:
Pitch Black SS wrote:
Just going with the hundreds of w-body owners that have tried Bosch sensors only to have issues. Same things with spark plugs.

Will Bosch sensors work? Possibly, but after 10+ years of dealing specifically with W-Bodies, I can count on 1 hand the amount of successful Bosch O2 sensor installs.


well, feel free to add me to one of those fingers


luck of the draw I guess. I have had 2 Impalas and never had some of the common issues that others have.

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The_maniac
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PostPosted: Mon Jun 13, 2011 8:52 am    Post subject:   Reply with quote

FYI - I installed a BOSCH downstream O2 on my wife's '05 3400 Impala in December, so far NO problems. I've used BOSCH O2 sensors on 3100's with no problems. But, those are un-modified cars and just one person's experience.

As for the OP's problem, an aftermarket CAT should be fine. If this is supposed to be a "stock spec" CAT and O2 sensor, I'd zip back to the shop and make THEM correct this P0420 condition. It sounds to me that something is wrong with the parts OR the installation.

If it's a high flow CAT, then I would look at other solutions (such as deleting the code from the PCM or the spark plug anti-fouler).
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PostPosted: Mon Jun 13, 2011 10:49 am    Post subject:   Reply with quote

The_maniac wrote:
FYI - I installed a BOSCH downstream O2 on my wife's '05 3400 Impala in December, so far NO problems. I've used BOSCH O2 sensors on 3100's with no problems. But, those are un-modified cars and just one person's experience.

As for the OP's problem, an aftermarket CAT should be fine. If this is supposed to be a "stock spec" CAT and O2 sensor, I'd zip back to the shop and make THEM correct this P0420 condition. It sounds to me that something is wrong with the parts OR the installation.

If it's a high flow CAT, then I would look at other solutions (such as deleting the code from the PCM or the spark plug anti-fouler).


Cheap "universal" sytle cats do have failure problems on these cars. I've had two Impalas, the first was an '01 3.4 and I tried the cheap cat route with it.....failed within a month. When I finally spent a bit more money and bought a OEM replacement from a reputable company it worked for the next 3 years until the girlfriend of the person I sold the car to wrapped it around a tree, at which time the cat was still operating properly, unlike the driver.
I would agree that some discussion should be had with the shop that installed the cat....isnt there some federal emissions law that holds them responsible for repairs such as that?
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PostPosted: Mon Jun 13, 2011 12:33 pm    Post subject:   Reply with quote

DennisW wrote:
Cheap "universal" sytle cats do have failure problems on these cars.
....
I would agree that some discussion should be had with the shop that installed the cat....isnt there some federal emissions law that holds them responsible for repairs such as that?


It does not come as a surprise that not all aftermarket cats are equal. But sounds like you agree with me that the shop has a responsibility in helping the OP resolve this.

It's as simple as you took it to the shop for a repair, you walked out and still have a problem.... A problem that guarentees you will fail your local emmissions test. You should not have to spend more time and money to get a "work around" assuming this is to be a stock spec replacement. That's just not acceptable IMO.
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rpm1200
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PostPosted: Tue Jun 14, 2011 12:11 pm    Post subject:   Reply with quote

Thanks for the input everyone. I don't know what brand the cat and sensors were (they were replaced together by the shop), but I still have a copy of the warranty card from the cat so I can determine who made that at least.

I figured since it's been 9 months it would be considered my problem at this point, but it can't hurt for me to take it back to the shop and see what they say. If they want me to spend my own money on new parts I will definitely not go for it...
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PostPosted: Tue Jun 14, 2011 10:02 pm    Post subject:   Reply with quote

Ah, I did not catch the length of time that passed.

BUT, I'd be curious of the warranty on both the O2 sensor and CAT (if they have a 1 year warranty), so if the shop has to swap them, you may only get dinged on labor since it's been about 9 months. Better then full price.
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PostPosted: Tue Jun 21, 2011 7:30 pm    Post subject:   Reply with quote

FWIW, all cats are not created equal. They can say what they want on the box to make the sale, but some cars are just more sensitive to cat replacement than others. The Impala being one of them from what I've read, which is a bummer Sad

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