I took my Fabia 1400 16 v for its MOT last week, the engine management light had been on for a day - Id had the car serviced a week before - the MOT failed on emissions.

I booked the car in at the main agent and they said it need two sensors replacing. Had that done £217. Took my car back for a re test and the MOT guy says the emissions are higher now than last week!:eek:

Ive rung the main agent and the car is going back again tomorrow. But I cant see how this could be? They must surely have tested the emissions after they did the sensors to ensure that all was fine wouldnt they?

sounds as if the cat has gone, to say it's failed twice cant be good.

unless the ecu has changed a few settings?

Hi there andy, I did add to another thread for someone with similar probs, but Ill repeat here as it may help someone with the same happening.

I rang the main agent in a slightly mad woman way and they told me to take it back next morning.

They gave me a lift home and then rang in the afternoon and sent a car to take me there. They had stripped and cleaned egr valve and pipes, stripped and cleaned throttle body and then put it through an MOT for me - all passed - everything AOK. They even repaired a puncture in my spare tyre for me and didnt charge me for any of it - said "goodwill" and yes, it has earned them goodwill, and in about 9 months I shall go back for my next car.

So did you actually need the sensors ,or would this work have made the car pass the MOT?

Well, the sensors were coming up as faults on the engine maintenance thingy - but whose to know? Im not a mechanic, so ...................

Result for you then.

The dealer has restored your faith on Skoda then, depite the car causing you grief.

Well yes, I mean they sorted it and sorted it quickly and went the extra mile, so I cant really complain. Im just happy my little car is now sorted.

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The following may be of interest:-

O2 Sensor Strategies: Unheated one- or two-wire O2 sensors on 1976 through early 1990s applications should be replaced every 30,000 to 50,000 miles to assure reliable performance. Heated 3 and 4-wire O2 sensors on mid-1980s through mid-1990s applications should be changed every 60,000 miles. On OBD II equipped vehicles, the recommended replacement interval is 100,000 miles. The O2 sensor’s responsiveness and voltage output can diminish with age and exposure to certain contaminants in the exhaust such as lead, sulfur, silicone (coolant leaks) and phosphorus (oil burning). If the sensor becomes contaminated, it may not respond very quickly to changes in the air/fuel mixture causing a lag in the PCM’s ability to control the air/fuel mixture.

The sensor’s voltage output may decline giving a lower than normal reading. This may cause the PCM to react as if the fuel mixture were leaner than it really is resulting in an overly rich fuel mixture.

How common is this problem? One EPA study found that 70 percent of the vehicles that failed an I/M 240 emissions test needed a new O2 sensor.