One I made Previasly

I have a 2002 Toyota Previa, purchased through, and regularly serviced by my local Toyota dealer. The car and the dealer have been excellent so far and the car is now in its 3rd and final year of extended warranty from Toyota. Yesterday a dashboard warning light came on which indicated I had to take it to a service centre. The diagnostic check showed a faulty sensor in the exhaust, which was found to be seized in place when the dealer tried to replace it. This means that the entire catalytic converter needs to be replaced instead, which will cost in excess of £800. So far, the warranty company has said that they will only pay out for the replacement of the faulty sensor, not the catalytic converter. They have agreed to refer it to Toyota GB’s technical department for a reply. The dealer has been extremely supportive and maintains that I should not have to pay for a new cat when the sensor is the faulty part. The warranty contains a paragraph about ‘consequential damage’ but I’m not entirely convinced that this applies here. Can you offer any advice?

Asked on 28 August 2010 by MG, via email

Answered by Honest John
Technically the mechanical breakdown insurer is in the right here. The cat converter suffered no breakdown. The problem was simply that the lambda sensor could not be extracted. Now I happen to have met someone who solved this sort of problem. He explained to me that lambda sensors are brass, screwed into the cast iron manifold. They have to be, otherwise they would simply fuse to the red-hot manifold. The problem with brass is that it is relatively soft, and a conventional spanner does not grip the flats of the nut tightly enough. So this chap developed a spanner that does. It's possible that if the cat converter is not already damaged and the flats of the nut are not already too rounded off, the sensor can be extracted with a better spanner.
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