Andy Burns wrote:

VanguardLH wrote:

I wonder how a car knows a gas sniffer is poking up its ahole. Oooh,
warm that up first before sticking it in. I suppose the car's computer
could notice the car wheels weren't rotating when the engine got revved
up and the steering wheel wasn't turning.

A bit more complex than that, but basically spotting conditions of the
standardised tests and switching into an alternate ECU mode

https://media.ccc.de/v/32c3-7331-the_exhaust_emissions_scandal_dieselgate

Jump to 57:00 if you just want the money shot, but the whole thing is
worth a watch ...

That was interesting. I jumped to the timemark, but decided it was too
much out of context, so I watched it all. Interesting how the
alternative model was used for most of the driving (underdoses the NH3
to convert NO) but switched to the main model during the conditions of
NEDC testing. Man, they sure are tricky. Also interesting is that VW
isn't the only one, but BMW was caught a decade before but managed to
silently alter their model. Apparently lots of brands do this trickery.
It's almost a requirement for the car to be road-worthy, but still pass
the emission testing for when the car is tested under nothing like road
use of the vehicle.