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On the way home from work the warning light came on!

What is that 2nd probe doin on the 1.8T, is in measuring the difference between the 1st probe ( measuring before cat) and 2nd probe ( after cat ) or is the second probe simply measuring if the cat gets too dirty?

Anyone got any ideas

For the guys with no cats, where did the probe get mounted on your exhausts???

I found it strange that the probe was in the middle of the cat also, usually they are after cats on cars are they not???

mine is not in the exhaust the second sensor it just under the side cover in fresh air light never come on! I just did that as i was getting the second sensor removed from the programming in stage 2 anyway so was not bothered , but have not had the stage 2 yet and lights never come on!!! The second sensor only checks the difference from the first, has no bearing on the fueling, been deep into this as i have no cat and checked the fueling and if anything its improved mixture etc! are you sure it is the second sensor thats bringing up the fault??

My money would be on that mate TBH. Had this problem before when i de-cated the car and the guy just put the sensor straight back in. So you reckon remove the sensor and fit a plug and it should be ok. Wasnt sure if the ECU is set up that if the difference is too high would throw up a warning light and if it was too low it would do the same. Been running the car a month now and thats it just come on! Gonna disconnect my battery to clear the light.

As for the comments about better mixture control - that is to be expected as these CATs need extra juice to keep them hot - what a waste of fuel!

As said already, the precat probe is the control probe and the postcat probe is just part of the car's (mandated) diagnostic equipment to check the exhaust emmissions.

Have you had the fault code(s) read? The dashboard light will go out after 6>8 engine starts after you have removed the reason for the fault.

Dont have VAG-COM mate to see what the code is

Thinkin of gettin the probe out and a blank put in, just wanna make sure it wont throw up the code againif emmisions are too clean!!!

mines been ok , for months now with the sensor in the mid air and its bob on!! wont cost you nothin to try it will it!!

Am gonna m8 at the w/e. ermmm total longggg shot but does anyone know the thread size for the probe?? Need to steal a S/ bolt from work.

here you go M18 X 1.5mm thats what you need!!!

Yer some man! lo, i'll get some tomorrow and cut them to suit!!!