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[Ralph M]

Does anyone know where I can buy replacement Catalytic converters at a discount price, because the pre-cats on my Omega 3.2 MVX 02 Reg saloon, are producing fault codes P0420/P0430.

Thanks

[bob.dent]

I suspect there's probably nothing wrong with the cats but a common problem on the 3.2 whereby the lambda sensors are playing up because VX put them in the wrong place. The only way to permanently cure the problem is to have them moved from behind the pre cats to behind the main cats. I eventually had mine done by Mark DTM and have never had the problem since. I'm sure one of the other tech guys will be along shortly to explain in a little more detail.

[Marks DTM Calib]

No and dont replace them.

The pre-cats are not important and the main cats will be fine.

If your very worried about the codes then get the post cat lambda sensors moved to after the main cats.

[aaronjb]

No and dont replace them.

The pre-cats are not important and the main cats will be fine.

If your very worried about the codes then get the post cat lambda sensors moved to after the main cats.

Wait, wait.. Vx put the cat-efficiency lambda sensors after the pre-CATs and before the main CAT? I guess someone was asleep at the wheel in design, that day!

[Marks DTM Calib]

No and dont replace them.

The pre-cats are not important and the main cats will be fine.

If your very worried about the codes then get the post cat lambda sensors moved to after the main cats.

Wait, wait.. Vx put the cat-efficiency lambda sensors after the pre-CATs and before the main CAT? I guess someone was asleep at the wheel in design, that day!

Nope, they had to ensure that they met the stringent start up emmisions for type approval, this requires a small cat mega close to the exhaust which gets hot very quickly.

We dont have to meet this for MOT's and hence as it starts to fail (it has a VERY hard life) we can move them

[aaronjb]

Nope, they had to ensure that they met the stringent start up emmisions for type approval, this requires a small cat mega close to the exhaust which gets hot very quickly.

Yep, I know all about preCATs (the MR2 has them - they tend to disintegrate and grenade the engine..) - but on the MR2 the 'cat efficiency' third lambda is after the main CAT, with the fuelling lambda sensors before any CATs, which seems much more sensible since - AFAIK - the requirement of OBDII is to monitor the efficiency of the main CAT or full CAT configuration, not the efficiency of the preCATs alone..

(Let's put it this way, the MR2 was designed to meet ULEV and only has three O2 sensors - two for fuelling before any CATs on bank 1 & bank 2, and one after the main CAT as sensor 2 bank 1.. Apart from J-spec imports, which don't need to meet OBDII specs - they only have the fuelling lambdas)

[Marks DTM Calib]

Nope, they had to ensure that they met the stringent start up emmisions for type approval, this requires a small cat mega close to the exhaust which gets hot very quickly.

Yep, I know all about preCATs (the MR2 has them - they tend to disintegrate and grenade the engine..) - but on the MR2 the 'cat efficiency' third lambda is after the main CAT, with the fuelling lambda sensors before any CATs, which seems much more sensible since - AFAIK - the requirement of OBDII is to monitor the efficiency of the main CAT or full CAT configuration, not the efficiency of the preCATs alone..

(Let's put it this way, the MR2 was designed to meet ULEV and only has three O2 sensors - two for fuelling before any CATs on bank 1 & bank 2, and one after the main CAT as sensor 2 bank 1.. Apart from J-spec imports, which don't need to meet OBDII specs - they only have the fuelling lambdas)

Chalk and cheese, this is a different scenario, design, setup, heavier car the lot.

Gm had to ensure they passed the EU test, the only way they can guarantee this is to ensure the pre-cats are upto temp fast hence they ARE monitoring the rights ones.

There would be no point monitoring after the main cats as it would take MUCH longer for these to heat up and the sensors to respond.....result, type approval fail! 

[2woody]

hey - get a load of you lot ...  "type approval", EU Emissions, OBD-II

now I am impressed

[feeutfo]

Does anyone know where I can buy replacement Catalytic converters at a discount price, because the pre-cats on my Omega 3.2 MVX 02 Reg saloon, are producing fault codes P0420/P0430.

Thanks

This is common on 3.2. Trust us, there is no need to replace the cats, it WILL pass the mot, it will NOT cause any running issues with the car, cats are about 700 sobs each, cheeper don't last.

Follow the guide in maintenance re moving post cat lambda, which is a good guide, but in effect, all it does in real terms is put the light out on the dash, local mech can do that if he can weld for a couple of hours work, some on here will do it for less than that.

Seriously, no need to change the cats.

[Entwood]

Another solution is to buy a cheap(ish) analyzer/resetter .. and when the light comes on .. just reset it. As long as it does not come back "instantly" there is no problem. I get this problem about once a year ... the GS500 quickly identifies the problem.. I turn the light out .. its fine for another year ..    GS500 about £80 ... less than Vx charge just to read the codes .. and probably less than a garage would charge to move the sensors.

HTH

[Ralph M]

Thanks everyone for the replies. I have tried resetting the fault codes by disconnecting the battery, but they return after a period and that period is getting shorter - currently down to 24 hours. Could anyone suggest who might help me to get the pre cat sensors moved? I live in Wilmslow, near to Manchester Airport.

[Kevin Wood]

Disconnecting the battery won't clear the codes with this ECU. They are held in non-volatile memory. You need to clear them with a code reader. Having said that, in the absence of a continuous problem the emissions light will turn off eventually.

Relocate the lambda sensors or ignore the light, IMHO.

Kevin

[bob.dent]

Thanks everyone for the replies. I have tried resetting the fault codes by disconnecting the battery, but they return after a period and that period is getting shorter - currently down to 24 hours. Could anyone suggest who might help me to get the pre cat sensors moved? I live in Wilmslow, near to Manchester Airport.

Although there may be other on here that are able to do this job, the only one I know is Marks DTM and he's in Nottingham. Might be worth a PM to Darth Loo-Knee as he does a lot of work on members Omega's at reasonable prices. Trouble is it's not a 5 minute job. Both sections of the exhaust with the cats and sensors on have to be removed, the sensors removed and holes plugged. Then new holes have to be drilled (requires a fairly hefty bench drill) and new boss's welded in place. Took a good few hours to do mine.

[feeutfo]

Ignoring the dash light is the cheapest and easiest solution, no doubt there 

Or dare I say it, remove the bulb....

Regular pedal tricks will spot any issues.

[TheBoy]

Just to add to this debate, your old, original cats will be far better (quiet, refined, durable, longer lasting) than brand new pattern cats.

As MDTM has said, moving the 2nd sensor on each bank to behind the main cat cures the code.


Again, MDTM is quite correct as to why the sensors are where they are.  Precats is probably a bad description, in fact GM call them 'Starting Cats'