Clutch switch. Why?

[CherryVimto]

I've taken this quote from another post so I don't clog theirs up with this question....

It sounds like the clutch pedal position sensor. If it is it should be attached to the top of the clutch pedal. It tells the ECU what position the clutch pedal is in I think

Does anyone know what, on the Puma, this switch actually does!?

A few years ago before I had 'discovered' the Puma and this forum, I had a Fiesta which developed running issues.
After weeks of research on forums, I found a piece of information relating to the switch on the clutch pedal. On the Fiesta, the switch was there to smooth out gear changes.

When I had fixed the running issues, I unplugged the clutch switch which made no difference to how the car ran.

Now, we know the Puma is related to the Fiesta and they share parts.
Obviously the engines are different... 1.25 in the Fiesta and 1.7 VVT in the Puma so they wouldn't necessarily share exact wiring looms either and the ECUs would be different/have different maps.

But how is it on the Puma this switch causes the amount of trouble that members seem to claim...?

 

[3dcandy]

The clutch switch is there for exactly the same reason on the Puma

 

[Wild E. Coyote]

The clutch switch is there to let know the ECU that driver depressed the clutch. Mind you, Puma has throttle cable, not fly-by wire throttle (fiesta Mk6 and newer are fly-by wire!). Also, Puma uses MAF, fiesta has MAP sensor and hence the running strategy of engine is completely different.
In practice it means that when you accelerate engine is usually running in open loop in regard to lambda and on rich mixture. When you depress the clutch and change the gear, the ECU will try to switch to lambda 1 (i.e. stochiometric) and run engine like that unless you depress the throttle very much (i.e. TPS doesn't tell ECU driver wants full power).
Without that signal from the clutch ECU might be a bit lost how to run the engine and you might experience the hesitation etc..
I am sure there is much more to it, but this would be a (very) short version.