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[VXL V6]

Trying to get a wiring diagram / pictures of the CAT / Exhaust system. My understanding of a Closed Loop emission control system is that there are sensors either side of the CAT but I cannot find any after the CAT - this is a 3.2 so it's slightly different to 2.5 and 3.0 I believe.

Was thinking of replacing the lambda sensors one at a time. Diagnostic tools say the error is generated from Sensor 2 bank 1 & Sensor 2 Bank 2 but of course this isn't necessarily the fault!

Original thought was duff CATs, emissions test proved they are good, second thought was dodgy petrol - well i'm on my third full tank now and it's still registering the code.

Any help appreciated!

[Kevin Wood]

I'd get the code cleared and see if it recurrs. I had a similar issue with the Morrisons debacle in February and it just went away after a few tanks of decent fuel. The fact that both banks are complaining makes me think it's not the lambda sensors themselves but something common to both engine banks - i.e. fuel, or a fuelling error caused by something else which is causing the sensors to go out of range.

The 2.6 / 3.2 does indeed have lambda sensors pre- and post-cat but the earlier V6's don't so check you're looking at the correct wiring diagram.

Does anyone know if sensor 2 is the pre-cat one or the post-cat?

Also, the actual code stored would be useful as there are several fault codes that the lambdas can throw up.

Kevin

[VXL V6]

Hi Kevin

Thanks for your help, the codes and emission lamp have been cleared 3 times now so concerned something is getting worse, it's reaching the 'threshold fault quicker each time.

The Codes are:- 'Suspect CAT for Bank1&2, not performing to full potential, code P0420 (Bank1), code P0430 (Bank2) - CAT threshold'

CAT's are good, Engine done 60K and in good health, agree with what you are saying about both cats at same time, wondering if there is a multi-plug that's not very good somewhere (heat related maybe?) but funny that all sensors appear working while diagnostic (Tech 2 / Sykes) readers are being used.

When you say decent fuel, do you mean putting some higher octane fuel in?

[JasonH]

Could someone have fitted 3.0 cats to your 3.2 ?

That way you'd be missing two sensors and the ECU would be complaining about it.

[VXL V6]

I guess anything is possible.

But it'd been absolutely fine for over three months......

Any ideas welcome because i'm running out of them! Doing a service at some point over the next week so i'll have a good look round while it's up in the air.

[Marks DTM Calib]

Hmmmm.....didn't we fix an airleak on your car, did the light start coming on shortly after?

It might be that the lambda block learn values had adapted over time to the airleak and fixing it has given a sudden change....it might recover in time or cna be reset as a test.

[VXL V6]

Hi Mark

The Emissions light first came on two weeks ago and I think it was about the middle of July when you fixed the vacuum leak so there's a fair gap of time.

The lamp has come on three times in total and been reset shortly after with the codes cleared, first two weeks ago, second one week ago and third two days ago, so it's getting more frequent now.

It's got to be something central to the whole of the emissions system as far as I can see. I think you'll agree that it seems to be running alright, certainly not running rough IMHO.

[VXL V6]

Well whatever it didn't like it's happy now.....

No emissions light this morning.....

[SP_3.2]

Hi VXL sounds just like mine my EML when out a few weeks ago and has not been back on. The 2nd senser would be the one after the can. the one before is on the bend just after the manafold. I was told that the sensors before the cat are diff to the ones after if that is of any help.If you have any more pros just PM me as i Know  a VERY good moble machanic who knows a lot about omeges and he is who i use when i get stuck very good guy and you can trust what is say,s.

Good luck man.

[VXL V6]

Cheers

The light hasn't come back on since (and the bulb hasn't blown either!) so will hold fire, the O2 sensors are about £71 each (genuine part) and the CAT's are £711 each (again, genuine part) so every possible cause has to be eliminated before you start spending those sorts of figures!!!!!

Fortunately all of the above is proved pretty much beyond reasonable doubt to be ok. One advantage of the 2.5 / 3.0 over the 3.2 is that 2nd hand CAT's are much easier to obtain.... guess that will change over time.

Just hope it stays off now!

[Martin_1962]

I had emmisions light on with worn plugs

[VXL V6]

That's interesting, will be changing them when I service the car so that's one less thing.

[TheBoy]

2.2/2.6/3.2 all have lamdas before and after cat.  2.0/2.5/3.0 dont/