My ECU light had been on a few weeks and I took it to garage this week to be checked and for MOT. The garage have told me my CAT and sensors have failed and need replacing (for a huge cost). However, they said the emissions are fine and passed the MOT and there are no symptons/problems. Do you think they are right or could the sensor just be gone? Can the ECU tell the difference? Do I ned to replace it if there are no problems? Also, any idea where I can get one - I've tried cats4less etc but it seems to be dealer only.