CAT light came on and car died today.

[Mr K]

when my lamda sensor failed (and it failed to the point i cooked the cat good and propper!) the car drove pretty much exactly as before, so i suspect your cats arn't at fault as you say.

The engine speed sensor would make sense - as it sudden thought 'oh, the cranks not going around' so stopped the fueling. A friends BMW had exhaust the same (random stalling) due to the same sensor.

However, i would still clear and rescan the lamda errors if it does turn out to the crank sensor. When mine went the failed lamda error sat in the memory of the ECU without the engine management light on, this meant i drove around for ages with it putting excess fueling down the right hand bank, inturn i burnt out the cat. It wasnt until the cat got so bad that the lamda after the cat that was still functioning (you have 4, one sensor before and after each cat.) picked up that the cat was no longer 'in range' due to being so knackerd that the light came one!
The result was that instead of £150 for a lamda to fix the job, i needed a cat too! which are £770/700 from audi depending on which side, or £300-330 for the one and only factor i could find (assuming your facelift). Wouldnt want that to happen to anyone else!!!

[Mick]

Thanks for the input.

I'll get a sensor ordered and see where it goes from there.

I'm also thinking of de-catting but need to look into lambda sensor issues that would arrise from that but that's for another day.