Our car nearly failed it s MOT due to exhaust emissions. The item that nearly reached its upper allowed limit was the Lambda reading although the other values were about normal. If the lambda sensor needs replacing is it very expensive and much work involved? Could it be a link with that contaminated fuel from Tesco recently?
The lambda sensor measures the oxygen concentration in the exhaust gas and is usually screwed into the exhaust pipe a few inches down from the exhaust manifold. They are easy to replace and the cost depends on the make of car. I got the job done for �25 on my L-reg Ford Fiesta.