Hi, I'm having an ongoing problem with my 2002 2.0 Mondeo lx and it's frustrating me no end. Basically the engine management light came on a while ago so I plugged in OBD (on board diagnostic) machine and it showed up with the code P0420 which it says is a fault at the catalytic converter system/bank 1 and the effeciency is below the threshold. I have changed both the lambda sensors but the problem still exists and the same code comes up.
Could there be a problem in the wiring or somewhere in the system?
Please help! Many thanks in advance.