As of my previous post I plugged it into the car and it come up with fault code P0420 Catalyst system efficiency below threshold I erased the code had no problem since (touch wood) can anyone shed some light on the fault and what to look out for ?

Thanks Sam

 

Probably nothing to worry about, my forester threw the same code once but never came back.

If it comes back it could mean your cat is shot or the O2 sensor on its way out, but more likely its just a blip.