Error code cause ???

[craig79]

Hi all, my question refers to my earlier post re. my engine management

light. Had my brother over with his diagnostic meter earlier. Got a PO420

error code. It said something like " catalyst efficency threshold eceeded "

Anyone have any ideas of possible causes ???

P.S. Have a high flow d/pipe fitted which obviously gets rid of the front cat

in case this helps any ?

Cheers,

Craig.