oh dear,its a garrage job iam afraid.the car will have a code stored in obc and can be read using a diognostic code reader.the code is related to a specific component eg probe/sensor.or the filter/housing.try a reputable garage for the reading,around 20 quid or so.main dealers 90 quid plus.if it turns out to be a sensor/probe you can easily fit yourself .
tranny granny, December 2011