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Vauxhall Corsa Z10XEP 2008 - O2 sensor fault, code P0420 #

Posted by Dave Emm on October 14, 2013, 8:09 am

Year of Manufacture *: 2008
Engine Size and Code *: Z10XEP 3cyl
( Optional) Fault Codes: p0420

This vehicle came to us in August with a O2 sensor fault which turned out to be a cracked exhaust manifold. The manifold/cat (Unipart) was replaced along with the front O2 sensor,it has now returned to us after 2 months with mil on and code P0420 cat efficiency below threshold. Gas test extremely good, no vac or exhaust leaks, blanked off egr, no change. Scoped rear sensor and after an initial warm up period its trace follows very closely that of the front one suggesting that the cat isn't working but the gas test says it is. Have checked for ECU updates with local dealer but nothing available. The engine runs ok albeit a bit gutless, any help would be most appreciated, cheers Dave.

Re: Vauxhall Corsa

Posted by tony bickers <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5143' width='330' height='300' border=0 style='border:none;'> on October 14, 2013, 12:06 pm, in reply to "Vauxhall Corsa "
Tony Bickers

Think you have answered your own question Dave, only long term cure will be a genuine cat

Re: Vauxhall Corsa

Posted by Dave Emm <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2827' width='330' height='300' border=0 style='border:none;'> on October 15, 2013, 5:01 pm, in reply to "Re: Vauxhall Corsa "
David Emm

Thanks for your reply Tony.I was under the impression that all cats have to come up to a certain standard these days,I wonder how inefficient a cat has to be % wise before it causes the mil light to come on.The owner was desperate to use the vehicle so she's had it back for 4 days now and the light has stayed off but I'm sure she will be back at some point as we did'nt actually do anything to cure it. Cheers Dave.

Re: Vauxhall Corsa

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on October 15, 2013, 5:54 pm, in reply to "Re: Vauxhall Corsa "
Peter Mutlow

Hi Dave,

There has been plenty of discussion on the standards of Cats on UKAT. They had to comply with an EEC Standard (last year I think) but even then there were exceptions to the these standards. In other words, a Cat can meet these standards and still not be up to the job. To save time and any misunderstanding, I always insist a Cat is fitted from the Main Dealers otherwise I am not interested in any repercussions.

However..... I am interested on how the post cat sensor is mirroring the pre-cat sensor which as you rightly say means the Cat is inefficient but the emissions were all within spec. I would have thought they would be outside spec to prove the inefficiency of the Cat. I hope that a "learned" friend will come along soon and explain why my assumptions are incorrect.

Regards

Pete M

Re: Vauxhall Corsa

Posted by tony Bickers <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5143' width='330' height='300' border=0 style='border:none;'> on October 15, 2013, 5:55 pm, in reply to "Re: Vauxhall Corsa "
Tony Bickers

Hi Dave,

The 420 code will be back, can take a month or longer to reflag that code.As to after market "type approved" cats, not worth the wrapping paper that they come in

.

Recently had an 01 Accord 2.0 in that flagged the 420 code on the way back from having a new downpipe and cat,managed 10 miles before the MIL came on and that was a Klarius type approved cat!

Re: Vauxhall Corsa

Posted by aidan birley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2879' width='330' height='300' border=0 style='border:none;'> on October 15, 2013, 7:16 pm, in reply to "Re: Vauxhall Corsa "
Aidan Birley

Hi

It is easy to work out how good an after market Cat is, just ask a local Pyki / gypsies how much they will give you for it. !!!

cheer Aidan

Re: Vauxhall Corsa

Posted by Dave Hill <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2783' width='330' height='300' border=0 style='border:none;'> on October 17, 2013, 10:26 pm, in reply to "Re: Vauxhall Corsa "

>>It is easy to work out how good an after market Cat is, just ask a local Pyki / gypsies how much they will give you for it. !!! <<

I have used that argument myself a few times Aidan

Anywhoo...

This is an old topic now & most should be up to speed on it.

Here is an excerpt from a case study that I wrote for Pico a good while back.....

Quote...

As of August 13th 2009, a new regulation came into effect that makes it an offence in the UK to sell or install a non-approved catalyst to a car or light commercial first registered after March 1st 2001.

...End Quote

Take a look at the full article....

Link: Catalyst efficiency Pico Style

Re: Vauxhall Corsa

Posted by Bryan Smith <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5330' width='330' height='300' border=0 style='border:none;'> on October 27, 2013, 9:36 pm, in reply to "Re: Vauxhall Corsa "
Bryan Smith

>>It is easy to work out how good an after market Cat is, just ask a local Pyki / gypsies how much they will give you for it. !!! <<

Not heard that before but love it and very true lol.

Re: Vauxhall Corsa

Posted by dave emm <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2827' width='330' height='300' border=0 style='border:none;'> on January 7, 2014, 11:19 pm, in reply to "Re: Vauxhall Corsa "
David Emm

This vehicle eventually came back with the same fault. Obtained a replacement cat from Unipart and noticed that the new one was far better quality than the previous one they supplied ie ceramic core as opposed to metal. That was a couple of months ago so it seems all is well now. Have read all replies and I understand how the rear sensor monitors the efficiency of the cat but as Pete Mutlow says I still don't under stand why a cat which is producing a perfectly acceptable set of exhaust gas figures should throw up the P0420 code. Cheers Dave.

Re: Vauxhall Corsa

Posted by Mark Shipman <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3635' width='330' height='300' border=0 style='border:none;'> on January 8, 2014, 8:41 am, in reply to "Re: Vauxhall Corsa "

Hello,
My understanding of this is when vehicle goes into closed loop emission control, the "cheap"/aftermarket cat has not reached operating temperature therefore the downstream lambda mirrors upstream , continued driving/MOT test procedure will eventually "light" the cat and make it work efficiently to pass the MOTC/give a weaker mixture to downstream lambda.(Im thinking the ceramic will warm up quicker/give even heat distribution
Maybe im wrong but thats how I explain it to my customers.
MARK

Re: Vauxhall Corsa

Posted by Mark Carter <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on January 8, 2014, 4:12 pm, in reply to "Re: Vauxhall Corsa "
Mark Carter

The EOBD monitoring "cycle" is different to our MOT test standards and accesses the OSC of the CAT under different conditions.

Mark

Modern cars, Its all wizardry and witchcraft

Re: Vauxhall Corsa

HA!
I think that's what I was trying to say in a round about way!
MARK

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