Hi there had a car in today for mot but customer said engine light comes on now and again and was on when he arrived . Scanned It for him and fault code p0420-09 was present (catylist below threshold . Proceeded to do mot and all was fine emission readings were CO 0.09%. HC57PPM and lambda 1.00 . At idle CO was 0.02 %=Rescanned it and looked at data @2000 rpm pre cat sensor was 1.5 v and post cat sensor was 0.5 v on graph they were basically mimicking each other had to pass it coz all was ok but he said he will want it looked at .i haven’t come across the -09 bit after this code before can anyone offer any help
Thanks in advance
Ian