I recently bought a 2001 A6 2.8 Quattro 70k miles ... I notice some exhaust or burning smell when I park the car in my garage... while driving on 70 or up i also smell slight exhaust sometimes... someone told me that german cars have catalytic converter and its normal...
after few days of driving check engine light came on... Took it to Autozone and they told me that my rear O2 sensor bank 2 is bad or something... when i tried to look up online to buy the parts i found atleast 6 different O2 sensor for 2001 A6 ... i m not sure if its really the O2 sensor or the exhaust leak ... just wanted to know if anyone have any suggestions how best this should be addressed....

 

You should be able to hear exhaust leak.

 

Thanks for the reply... my another question is what If I dont replace the O2 sensor ? Can it cause damage to other stuff? The check engine light comes on for few days and then goes away... should I replace it or wait for it to completely goes bad...

 

"I notice some exhaust or burning smell when I park the car in my garage"
Perhaps the smell comes from the oil dropping over the exhaust - valve covers-cam adj seals.
Very common issue => search for oil leaks on the forum.
Yes, German cars have catalytic converters and many more things, many of them go wrong separately or simultaneously at any given time.
There are some patterns of failures and maintenance activities that are quite extensively discussed here.
Get familiarity with the car; (manuals –Bentley; scanners –VAGcom, etc)
Find somebody you could trust and rely for repairs => this is the hard part of the ownership.
You have always the option to ignore the CEL and drive till something breaks - be careful with the TB though. It’s all about your risk tolerance (as with gambling and investing).

 

Fortunately the rear sensor is not as critical as the front sensor. But as with any other things in cars (and life), take care of it when you get a chance.

But before you take any actions, what was the actual code that was pulled?

 

Sorry I have not got time to go back to autozone and get the actual codes.... will do that tomorrow

 

the code is P0150 and it says Bank 2 Sensor 1 ckt malfunction

 

ank 2 sensor 1 is precat correct guys? Its probably an oxygen sensor, the front one. If a 02 is giving bad readings the engien defaults to a rich a/f table. You might be smelling gas because the engine isn't burning everything in the cynliner because of the 02. At 70 000 I would be expecting a replacement soon anyway.

 

now the question is should i replace both sensors or only the one that is giving problems... if its precat that means its more imp to replace it ? someone told me if i dont replace it soon it could cause damage to my cat converter ? is that true?

 

Yes, the sensor 1 controls the mixture and you should take care of it. If you want an hones opinion about which sensors to replace, I actually would recommend replacing all 4 sensors, but 2 at minimum.