Hi Lee

I think the point that Sanjay is trying to make is that the Toyota's he had ALL passed an emission test
but had flagged a P0420 code because as Mark stated after 12 years the cat may have degraded slightly but is still MOT legal

The original ECU software parameters were set a little on the tight side, so a MOT legal cat that has slightly degraded would bring the light on

The software update will widen the parameter slightly to accommodate a slightly degraded legal cat

Probably not a permanent fix as the cat may still carry on degrading and eventually fail and MOT test

Many sofware reflashes or upgrades are designed to accommodate for parts / engine wear over a period of time, the design engineers cannot predict what will happen to an engine over say 5-10 years, or they may have got their sums wrong first time around

Sanjay was not implying that its a fix for a dodgy cat (MOT failure)

Think that sounds right

Peter