Diagnoising Catalytic Converter Failure

[bassplayer_uk]

Hi All,

I've just booked my car in with a suspected cat failure. The car is showing the 'catalytic converter below efficiency' fault code (Its a single cat car). I trust my garage I think but was surprised by their attitude to diagnosing the problem. I've read online that its crucial to track down what has caused a cat failure e.g. failed Lambda sensor, Faulty injector etc. My mechanic pretty much said anything like that would be shown as a fault code itself and pretty much said he wouldn't need to check lambda sensors etc if there was no code.

Does anyone know if its safe to diagnose a cat failure just by the presence or absence of other fault codes on the vehicle? The guy is talking about the engine having simply been over filled with oil. How common is this and how likely is it to cause a failure?

Many many thanks for ANY help or advice you can offer.

Darren.

[RickT]

when the cat fails/ breaks.. the porcelain inside it begins to rattle like crazy while your driving.. A mate of mine's CAT went and there was no performance changes apart from rattling away as he was driving? - (obviously the emissions were not checked)

sorry i cant help any more?? -

ANYONE GOT IDEAS??