I have a VW jetta VR6 2001, 2 months ago I had a check engin light went on, so I went to see the man who always fixe my car, he did use his computer to check on the systemthenevery thing went backto the normal.

After 2 weeks same problem came on again andmy man did thesame thinghe checked on the system like he use to, the same message came on his computer ( P0420 catalyst system, bank1Efficency below, fault code report: fault code is 16804 ) so we don't know whatto do with it so please if you know something that could help please, help us to finish with this problem.

 

Did he ever change the O2 snesor?? Bank 1 would the O2 sensor in in front of the cat..if I remember right... I think most cat codes are from the O2 sensor. Now Vw did have a recall about certian sensors going bad, giving codes like "exhaust sytem below threshold", or something like that. All they do is remap your ECU, and it wipes out that code and the old programs installed for the system.