Hi,

I own a 1.2 VW polo (52 plate).

Since I've owned the car it has repeatedly come up with a check engine light, the code being p0420 (Catalyst System Efficiency Below Threshold (Bank 1)

I have changed the front oxygen sensor and coil packs then finally decided to take the car to VW after a local garage couldn't diagnose it any further.

VW diagnosed my vehicle with a broken catalytic converter! They quoted a repair of £1,200! (More than the car's value).

I phoned a local VW specialist who quoted £750 (genuine parts).

Local garage £250 (non-genuine parts)

My question is, can I use an after market catalytic converter or should I be using a genuine part?
If I use an after market catalytic converter will this soon fail on me too?

Thanks,

Kate :)

You should be ok using an aftermarket cat as long as there isn't an underlying cause as to why yours has failed. For example if the car is burning lots of oil.

You say you changed the front lambda sensor but did you change the post cat one too? As surely that would be the one detecting a faulty cat and therefore throwing up the error code. If the sensor isn't working right then it might throw up the same code.

If it were me I'd try the sensor first as its the much cheaper option.

Thanks for the advice.

The car isn't using up a lot of oil, has no visible leaks and doesn't use anymore petrol than another car of it's size.

Might go ahead and try lambda sensor 2 as it's a bit cheaper to get done

mine did this from time to time, i noticed that it did it less with th more expensive petrol, i didnt mindrunning it on this, i know its not a ferrari but it ran nicer and got a bit more mileage.

do you use the same petrol station all the time?

also, have you looked at second hand ones? there are a few on ebay for a lot less then the cheapest quote you got.

failing all that, you can get a "spacer" for the front lambda, this puts it further back out of the cat, meaning it reads less. these are normally used on cars that have the cat removed. i haven't tried it on the 9n though.

£1200, what...

I would try CATACLEAN first, £12 a bottle and might sort out you issues. Then go down the road of a second hand unit.

Have you had the codes cleared? Does it just come back?

Yeah I do usually use standard esso fuel.

Yeah that's an idea to get second hand parts on it.

I haven't tried cataclean! I will give that a shot thanks!

I ended up buying some after market "vagcom". The code always comes up with: p0420.. When I delete the code it will usually come back on after about 100 miles of straight motorway driving.

Recommend http://www.cats2u.co.uk Get a type approved CAT. They can also arrange local fitting too with great prices.

PoloD.

As above cats2u have the best prices around!

I was going to buy one from them but then I tried cataclean and it fixed my problems .

Hope it helps you, let us know how you get on.

Okay great!

Car is in the garage today getting the 2nd lambda sensor done. Hopefully that will solve my issue! If not looks like it will be a new catalytic converter :(

Thanks for all the responses!

When my Lambda went, my diagnostics threw up several codes just for the one lambda!

So i think it could be your CAT that's at fault but I hope changing that second Lambda works for you tho.

Did you you try cataclean?

I'm going to try put some cataclean in once I pick the car up in a bit. Hopefully that will improve it.

Going for a long drive on the weekend so I'll see if the fault code comes back!

If not looks like it will be a cat... :(

Good luck! ; )