Hi All

New to this forum so Hope Im in the correct area.

I have an Audi A4 2.0L 2002, its got this fault code

16804 - Catalyst System: Bank 1: Efficiency Below Threshold
P0420 - 001 - Upper Limit Exceeded

I have looked at this and other forums and see a lot of them talking about a leak in the exhuast system but I dont think I have a leak so I ran a log on veg to see what is going on.

So a few questions regarding this

I see another code (16816) shows bank 2, is bank 1 one of the lambda sensors and bank 2 the other? if so which is which?

I have attached a zip file that has the log in it. within the log file it shows 2 lambda sensor values one on measuring block1 this value varies between -5.5 to 15.6 are these figures correct and acceptable?

the other is on measuring block 6 this one contiually shows -1.6 I assume this is not correct?

Is this reading likley to be why I am having the this fault code and is it likley to be as simple as changing the one U\S sensor?

Is there any way of testing the lambda sensors?

I have had an intake air leak on the engine but have now fixed this, I also had the g28 engine speed sensor fault also fixed today.

Thanks in advance

Harry