Hello, My 02 Focus ST170 has failed the MOT on the emissions. The engine management light has been on for a while and does not seem to affect running it at all. The light will go off sometimes and then comes on again. The garage code read and said its on eof the 2 lambda sensors or the cat. I ve replaced the pre cat sensor and the light has come back on again. Is there anyway of telling whether it will be the other sensor or the cat? The post cat sensor is something like £80 and i ve already £60 on the pre cat one. Any help much appreciated.
Sam