Can anyone help me my engine came on and had a buddy run a scan and problem code P0420 came on which Catalyst System Efficiency Below Threshold was the problem on the car. What can some of the common problems be with this error and should it be something I should get looked after sooner than later? I have 2006 2.0 A3 132k . Any info would be appreciated.

 

It may be your O2 sensor.

 

Thanks Mike , hoping its nothing to expensive or costly bad time of year !!

 

As you mentioned their must be fault in the catalytic converter which should be replaced... A new one will cost you round about $600 to $1000 or contact to the car repair shop..

Well this happence due to emissions issue and not the performance.. Well catalytic converter is one type of burner which residual the fuel vapors in the exhaust..