Back in the the 80's
My Ford RS Turbo had an interesting factory fitted switch under the bonnet. It was curious as there was no engine bay light. Well I by chance found myself on an off site training course and happened to be sat next to the chap who designed the ECU. Apparently the purpose of the switch was to inform the ECU that the car is in an emissions or approvals test as the bonett was raised. It set everything to be as clean as possible in this mode. When the bonnet was down, it changed the parameters to be more performance orientated with less emphasis upon emissions.
Nothing much has really changed in 30 years other than the ability of the ECU to autodetect it is under emissions testing.
Biting the hand that feeds IT
