Dealer telling me that p0420 means my o2 sensor is bad but I'm sure there's a change it might be the catalyst system

[Aranshaw]

Well basically here's a recording of the call I had with him

http://vocaroo.com/i/s1TcAUIQa1Ms

Please take a listen, I've had the car little over a week and the engine light came on and my reader said p0420 on it and from what I've read it means "Catalyst System Efficiency Below Threshold (Bank 1)" this can sometimes be caused by a bad o2 sensor but he's saying its a sure thing, please give your thoughts. I really don't know much about cars as you can tell!

Cheers

 

[Scooba_Steve]

Who cares, give it back to them to fix at their cost.

If they replace and light gone, happy days. If it comes back, same problem, they can fix again. If they don't fix it, give it back again.

 

[Mark555]

I assume you bought the car from a dealer? If so, one of the reasons you paid a premium price above what it would cost from a private sale, is to cover a warranty usually between 1 and 12 months. They are required to fix the problem under the Sale Of Goods Act. If you get the same problem occurring, even after the warranty expires, they still have to rectify it. If, after 3 attempts, the problem still exists, return the vehicle and get a full refund. You can also request reasonable expenses for back and forth to the garage.

 

[andyfanshawe]

Its certainly not a "sure thing". To be confirmed, the waveforms of the o2 sensors have to be checked. I put propane in the intake while engine running to see if both pre cat and post cat sensors react along with short term fuel trim.
An oxygen storage test on the CAT can be done that can confirm or deny.
Watch this for brilliant advice https://www.youtube.com/watch?v=vyVnhCIMDnw

Ive been down this road many times before. I have saved many a CAT by using CATACLEAN (including on my own Z4 last week or two). See my thread here http://z4-forum.com/forum/viewtopic.php?f=2&t=84224

Good luck.
Andy.

 

[Georgio]

I was getting intermittent post cat sensor errors which was usually after a supermarket fill-up. Stuck a bottle of Cataclean in the tank and the sensor has behaved ever since.
Supposedly cleans through the entire fuel system from tank, lines, injectors, sensors & cat, who knows, except the car certainly feels a lot smoother and more responsive.