O2 sensor again :( - Stealership won't cooperate

[[lot]]

Since Yesterday I noticed that my MPG went really low so I plugged my vag-com and here is the error:

16518 - Oxygen (Lambda) Sensor B1 S1: No Activity
P0134 - 35-10 - - - Intermittent

Now I know that this a bad O2 sensor and that it can be a bad Catalytic converter too.
I'm hearing also some rattling noise under my car from time to time.
I called the stealership today and the guy said to me that my catalytic converter has been changed already in 2005 and they refuse to do it again.
He said too that he's not sure that its really a bad cc and that I should bring the car to diagnose it (said it will cost approx one hour of labor 72$)

Could it be only a bad O2 sensor? in this case I'll buy a new O2 sensor and swap myself.
What to do if my Cat converter is bad and they refuse to repair it for free?
I have the letter sent by VW where it's written that the warranty is good for 10 years / 200k km

I should have bought the 1.8T

[SilverSportNOLA]

O2 sensors usually on most cars don't last too far past 100K Miles. So it is possible that is bad, and if running rich for too long could kill the cat, but it takes a while unless raw fuel is entering the exhuast.

[[lot]]

Originally Posted by SilverSportNOLA

O2 sensors usually on most cars don't last too far past 100K Miles. So it is possible that is bad, and if running rich for too long could kill the cat, but it takes a while unless raw fuel is entering the exhuast.

Thanks for the reply.
My O2 sensor was changed @120.000km. Now the car has 131.000km.
So you think I must change the sensor before killing the cat?

[Smileybug]

Beetles do have 2 O2 sensors. I don't know what codes go for what sensor but maybe your other sensor went bad?

One of mine started dying right after I got the car...and it had 55k miles on it at the time.