SpartanAudi

I took my q7 to the dealership for regular maintenance last Friday, I drove home and everything was ok. Later that night the engine light came on, since it was the weekend I took it to the local autoparts store and the code that they got was "P0420 Catalyst system efficiency below threshold bank 1"
Any ideas what that might be?
Thanks in advance!

iconoclast

most likely o2 sensor but if not new catalytic converter is in your future. not sure if you are in or out of warranty based on age or mileage but if so check to see if this falls under the emissions warranty (8/80).

SpartanAudi

I took it to the dealership on a Saturday; they tried to run a diagnostic test but were having technical difficulties. They told me to come back during the week so they could get Audi technical assistance. They must have reset the check engine light and it hasn't came back on. So I am not sure if I should take it back to the dealership or just wait for the light to come back on. I am still covered under the 8 year/80,000 mile emissions warranty.

iconoclast

without the light on or a stored code they won't be able to do anything.

SpartanAudi

the light has not came back on...maybe it was just a fluke?

jflow45

It takes about 80 miles or so of driving to come back... it's pretty likely that it will return.

SpartanAudi

So far so good...I think I have driven close to 200 miles since the dealership tried to check the fault...

Sjculkar

I went through the exact same issue with my 2012 A8L 4.2 I replaced my PCV valve and and oxygen sensor. After the problem showed up again after 100 miles, the Audi dealership replaced another O2 sensor and it's been great ever since.

One thing to note is that I found Audi Tampa sell 02 sensors online much cheaper that what they charge service for the same part! The Parts Manager dug his position deep and was not apologetic about how he sells the same part for 1/2 the price online that what he charges the Service Department. Service didn't know about this at all and they paid for my 2nd O2 install completely.

Check prices online, especially your own dealer e-commerce portal. It's the same part, same warranty but you may save a ton of money by having the part shipped from the dealership to you and bring in for service to install.