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sprinkles08
sprinkles08, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 22286
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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P0421 came on after changing all 4 o2 sensors, Yes and have

Customer Question

P0421 came on after changing all 4 o2 sensors
JA: Have you located all of the vehicle's oxygen sensors? Are the wires leading to and from each intact and in good shape?
Customer: Yes and have voltage
JA: What is the model/year of your Mitsubishi?
Customer: 06 eclipse
JA: Are you fixing your Eclipse yourself? What have you tried so far?
Customer: 3 8 yes been a tech for 20 yrs
JA: Anything else you want the mechanic to know before I connect you?
Customer: Prior ro changing all the o2 sensors i had codes for bank 2 cat. Eff. Now its moved to bank one
Submitted: 6 months ago.
Category: Mitsubishi
Expert:  Jerry replied 6 months ago.

Hello and welcome. My name is ***** ***** you for visiting the site, I am reviewing your question and will reply shortly, thanks.

Expert:  Jerry replied 6 months ago.

Let me just say that any money that you paid, or if you have a subscription, that money stays in your account until the answers are rated, (positive) regardless of how fast or how long it may take to get finished. You can FOLLOW UP AT ANYTIME, even after rating.

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There has been a factory service bulletin, for that type of concern. Warranty extension on the cats. If the recall for the PCM updates was done.

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Here is a link to what it states. You can copy and paste it into a new browser and rate the answer on this page.

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https://www.dropbox.com/s/n85b8iofg6wgzkz/CATALYTIC%20CONVERTER%20WARRANTY%20EXTENSION.pdf?dl=0

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Please don’t forget to rate the answer in a positive way, . EVEN IF YOU HAVE A SUBSCRIPTION ****THAT IS THE ONLY WAY I GET PAID **** Thanks

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Thanks

Customer: replied 6 months ago.
Originally bank 2 downstream sensor and castalist effency below norm. Change all 4sensors and codes went away and 0421 showed up
Customer: replied 6 months ago.
Recall was completed in 2007 accourting to mitsubishi
Expert:  Jerry replied 6 months ago.

I see, thanks. Do you think there is something other than either the cat or the software that is causing the code to set?

Was the software recall done on it?

Customer: replied 6 months ago.
all of it was done
Customer: replied 6 months ago.
Like i said the 0421 is the only code that showed up after changing them. And was new. All the bank 2 codes went away
Expert:  Jerry replied 6 months ago.

So the cats were both changed and the calibrations were installed in the PCM?

Customer: replied 6 months ago.
according to mitsubishi warranty dept. Called them directly because the dealer said there were no open recalls. They added that everything was done in 2007
Expert:  Jerry replied 6 months ago.

That is all I could think it would be on it, but wait there may be another expert who has more. I will opt out and open it back up. Please DON’T REPLY to this post as that will lock the question back to me, also DON’T RATE THE ANSWER yet, someone should be along shortly, I’m sure, thanks and sorry I wasn’t able to help with it.

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*******YOU CAN ALWAYS GET A REFUND WITHOUT RATING THE ANSWER AS BAD OR THE SERVICE AS POOR ********

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Expert:  sprinkles08 replied 6 months ago.

Hello and welcome to JustAnswer!

Do you still need help?

Customer: replied 6 months ago.
Still have same issue. Before i changed all 4 o2 sensors i had 2codes both for bank 2 one was an o2 the other for catalyst effent. After changing all 4 sensors the origional codes went away and a new code p0421 bank one catalyst effec. below normal
Customer: replied 6 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 6 months ago.
Engine performance from what i can tell is normal. I even tried spacing bank 1sensor 2 with 2nonfoulars.
Expert:  sprinkles08 replied 6 months ago.

Where did the sensors come from?

Did the problem start after any work was done?

Are there any exhaust leaks?

Customer: replied 6 months ago.
All are bosch exact fit and came from autozone. I bought the car a week prior and the engine light was on. No exhaust leaks. Ive been a tech for 20 years and never seen an issue like this
Expert:  sprinkles08 replied 6 months ago.

Bosch sensors will usually cause repeat issues. I'd recommend factory sensors.

There are only a few causes for a converter efficiency code. An exhaust leak can draw oxygen into the exhaust stream and set it, a lazy upstream sensor will set it, or the converter itself. By far the most common cause of a converter efficiency code is a failed converter.

Customer: replied 6 months ago.
how can the converter be diagnosed that it is bad so warranty will cover
Expert:  sprinkles08 replied 6 months ago.

You would check for exhaust leaks and monitor the switch rate of the upstream sensor with a scan tool.

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