Hi - thanks for the swift replies.

My Crossfire is just under 3 yrs old, so hasn't had an MoT test yet - so I'm unaware of what the emission readings are. There are no warning lights/indicators of any kind, in fact not even the "service required" icons have appeared (although just 10k from last service).

The two Cats in the middle of the car have gone, located in the centre of the car, under the transmission tunnel. I was hearing a rattle and had thought it was the rear end as I previously had my dealer fix those rattles.

I thought I'd get my local tyre and exhaust centre to check it out before I went back to the dealer. They said the inside of the cat had melted and was now rattling around inside the shell - they though it likely it was caused by a faulty sensor.

A few days later I has the dealer check it out- they confirmed the cats were gone and would be replaced under warranty - this will be carried out on Thursday. Should I be looking for the dealer/Chrysler to establish a root cause, rather than wait for another expensive repair when out of warranty? What I mean is - is Chrysler/dealer obliged to investigate the root cause of the failure so ensure it doesn't happen again - or are they simply entitled to replace the failed part and leave it at that?