I shall try your solutions tomorrow. Thanks. Where does the ECU get the information from to generates the code - the O2 sensor?. If so what is the probability of it giving false info. My car has done only 70,000 miles.
Could it be that the sensor is giving a false reading? I say this because there is no leak before the sensor which is easily seen and the wire to it looks fine. The exhaust pipe connection to the manifold is only a few inches above the sensor and can easily checked for leaks. Furthermore, the constant readout of consumption is normal (32 miles/gallon on short runs and over 40 longer runs). Very confused - plugs in good condition, idles smoothly with good acceleration and exhaust gas is clear. Also checked the area around the Mass Flow Unit for induction leaks and and air filter was changed a few months ago.
In view of what you say about excess air in the exhaust. What do you think about a faulty Exhaust Gas Recirculating Valve allowing air into the exhaust when it shouldn't? I say this because the light comes on at low revs, idling and low speed. It does not come on when travelling at speed.
Having read the function of the EGR it seems the gas flow is from exhaust to induction manifold above idling speed when working correctly. The opposite to what I imagined.
Have I got this right and is it worthwhile cleaning the EGR. Is it possible that fresh air can feed into the exhaust under low speed conditions?
Thanks Mat. I shall only get back to you if I have run out of ideas!!