P0420 Still and driving me BONKERS!!!

[AntSSSS]

Hi Chaps,

Posted this on VVOC as its for my Vec B - but as there are some knowledgable people here - thought I would also post here too :

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Hi Guys,

Ok - so my problem that is driving me bonkers! lol:

Car is a Vec 2001 2.2 150 Sri (z22se of course) as you know..

Basically - I keep getting the eml with: P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

I clear the code and then 10 - 30 or so miles later it will come back.
What has been done so far to recap:

- When I bought the car it had a brand new exhaust from the manifold back - so new cat, mid and rear box. This was producing the code as above

- I changed the rear box for a letterbox irmy exhaust. This was still producing the code - although I didnt expect this to change

- Bearing in mind the cat was brand new - I got two brand new Genuine VX Lambda sensors and fitted them. This was still producing the code as above, no change

- Knowing that the cat was not a genuine VX one and was a aftermarket cheapy one - I got a genuine VX one (all be it second hand) which had the pre cat removed and fitted that. This was still producing the code as above, no change.

- I then fitted a EGR cheater and blank from z22se.. this made a big difference to pickup and idle. But still the same code as above.

So I am now at a loss.. In a nutshell I have done everything I can think of to resolve this yet still its present.

It does seem to come on after a good 'enthusastic' drive, but never straight away - it seems to be after between 10 - 30 miles of the last eml reset.

I do run it on V-Power petrol only, and have never used anything else since I got the car.

So really after some help chaps as this is getting VERY annoying and the car is so nice to drive this lets it down.. MPG seems reasonable and there are no running issues.

HELP??

thanks Anthony

[chrisvectra]

blimey fella i thought you had solved this? what does appy say?

[AntSSSS]

at a loss the same as me. Said he would have done all I did and then unknown.

Vaux-Com says that the lambdas are operating fine...

Car runs SOOO well, not really too bothered, just annoying more than anything.

[benny]

you need to check the data list and watch what is happening with the two sensors and what the difference is .... if the code keeps comeing back check the looms from the o2 plugs to the ecu plug ...then if there ok it will be the ecu you will see this in the date list for the sensors ....

[AntSSSS]

you need to check the data list and watch what is happening with the two sensors and what the difference is .... if the code keeps comeing back check the looms from the o2 plugs to the ecu plug ...then if there ok it will be the ecu you will see this in the date list for the sensors ....

Hi Benny,

Ok - so using Vaux-Com I can do that..

Will check in a min and let you know for your advice if thats ok? Will check the reading and also the lean / rich reading also.

Appreciate your help.

A

[benny]

ignore the bank 1 part of the code it is only for v6 and v8 referance bank 1 has cylinder number 1 in it so bank one is only talking about the engine ...beeeing a 4 cylinder it only has one bank .... the first 02 sensor checks the engine fueling and goes rich lean rich lean back and forth when the engine is hot or what they term as closed loop the normal date fig is 0.40mv --900.mv ....so in real terms .4 of a volt to 9 volts ...the 2nd sensor will read the same but a much slower rate and sould be lean most the time but can flick between rich ....the 2nd sensor is watching the cat and checking it is working the code you have is put in when one of the sensors spots a fault ie the date is out of limits ..have you checked for air leaks on the inlet manifold this would give the same code .....

[AntSSSS]

OK - so findings as follows Benny:

As you say Sensor 1 switches from Lean to Rich and fluctuates from 0.4 to 900 mv when you rev it at a standstill, Sensor 2 reads the same sort of figures as Sensor 1, but always reads Rich... at least it did when on thr drive and I was reving it? Is that right??

I didnt actually drive it with the laptop on it.

Thanks in advance for your help.

[benny]

if sensor 2 is reading the same as sensor 1 i would think there isnt a cat in the pipe they sould read different ....! but if it has had two cats and your 100% they have cats in them that fill the pipe all the way round and have no cracks in the honeycomb it could be a wireing fault both 02 sensor wires meet by the gear change check here for rubs / damage .....if the loom is ok and the cats ...it may well be the ecu thowing a wobble inside ....

[AntSSSS]

You know what - you have me thinking, since putting the 2nd hand VX cat on its extremely raspy....

The CAT that I pulled off was a cheap one - like a kwick fit type job, this had a honeycombe in the neck of the pipe too where it met the manifold.

The second hand VX CAT I got DIDNT have that honeycome in the neck - which I am told is the pre-cat??? I wonder if the genuine second hand VX one has been 'played' with? or is it possible to get a Gen VX Cat without the precat (if thats what it is)? But as you say - I wonder if the main cat has also been played with?

I have a pic of what I am talking about, the new looking one (with the honeycombe in neck) is the new non genuine one:





What you think.. and thanks again!!

[benny]

have a peek in the bottom end and see if you can see the cat ...the pre cat is normally fitted on original pipes i dont think after market ones have them ....