My dad has been told his 55 sovereign 3.0 petrol has a faulty catalytic converter bank 1 and needs replacement but initial inquiries say the part is obsolete. What can he do Can anyone help please

 

I'm assuming you are in the UK and "55" means year? Based on what google tells me, I think that means the car is a 2005 or 2006 model, which is known as an X350. This forum is for XJ6 up to 1987. The forum you are looking for is here: https://www.jaguarforums.com/forum/x...-x350-x358-28/

However, if a code says catalyst low efficiency, have both the upstream and downstream oxygen sensors been replaced? If the catalytic converter has actually failed, try Eurojag in Darlington for a used part.