post cat or pre = code P0420

Jaycey001

As per title really, got EML on with code P0420 which says catalyst efficiency below limits and thinking its an O2 sensor but am unsure if its post or pre cat.

Does anyone know or do i have to put a live reading on each of them to find out?

No symptoms other than a very slightly rough pick up in first gear when light up.

Thanks for any advice!

James

KevinH

The code means that the sensors are showing similar readings, but they should be different (I think the front sensor should have a higher reading but don't quote me.)

You could try some Oxicat (pour into fuel tank) which will clean both Cat and O2 sensors.

Sjdickso

If its like mine its post cat, I get it all the time as I am running a 200cpi cat.

milo

Sjdickso said:
If its like mine its post cat, I get it all the time as I am running a 200cpi cat.

I've got no issues with running my 200cpi bud

Sjdickso

milo said:
I've got no issues with running my 200cpi bud

Think it depends on the quality of the cat. HJS Motorsport ones are meant to be the one to go for, everyone that had piper ones had eml's mine was from cobra sport again common with chucking up a eml.