On Mon, 21 Sep 2015 22:05:54 -0700, Jack Black wrote:

My question is HOW did the car *know* it was being *tested* for emissions?

http://www3.epa.gov/otaq/cert/docume...a-09-18-15.pdf

VW manufactured and installed software in the electronic control module
(ECM) of these vehicles that sensed when the behicle was being tested for
compliance with EPA emission standards. For ease of reference, the EPA is
calling this the "switch".

The "switch" senses whether the vehicle is being tested or not based on
various inputs including teh position of the steering wheel, vehicle speed,
the duration of the engine's operation, and barometric pressure.

These inputs precisely track the parameters of the federal test procedure
used for emission testing for EPA certification purposes. During EPA
emission testing, the vehicle's ECM ran software which produced compliant
emission results under and ECM calibration chart that VW referred to as the
"dyno calibration".