Hi have just had the cel/anti skid/cruise lights come on have plugged in code reader and it says p0420 i see this is a common problem whats the most likely cause ?.any help would be great. i`ve got a legacy 2.5 se  2003 

If you have a look in the how to section shoukd be a list of all the cides think it's under obd2 codes. I'll link it when u get home if you can't find it.