hi every one my brother is in durahm and i an in skelmersdale so i need your expert help again he has a problem with a missfire in low gears and i sent my code reader to him by post to check for fault code and PO136 AND PO141 THE HEATED OXYGEN SENSOR BUT IT HAS 2 1 BEFORE THE KAT AND ONE AFTER THE KAT how can i check thes senders it has a black wire grey wire white wire purple wire i have a good multi meter but dont know what wire go to the heater and signal for ecu any help as i will go over to help hem on sunday the code read as bank=1 if this helps thanks bazz