Cheating about pollution appears to be common
practice, not only Volkswagen did it
From
wikipedia
In 1973, Chrysler, Ford Motor Company, General Motors, Toyota,
and Volkswagen had to remove ambient temperature switches which
affected emissions, though the companies denied intentional
cheating and said that strategies like enriching fuel mixture
during cold engine warm-up periods could reduce overall pollution.
In 1996 General Motors had to pay a near-record fine of $11
million, and had to recall almost as many cars as Volkswagen's US
TDI diesels, 470,000, when they, like Volkswagen, programmed ECU
software to disengage emissions controls during conditions known to
exist when the cars were not being lab tested by the EPA.
There are more cases linked.