Originally Posted by BrApple
From what I read on the forums here the sensors in the Focus are self learning. This would be backed up with my friend putting SE 16" wheels on his ST, and not having to do anything with the sensors. And he doesn't park near the other set of wheels either.
Not quite, the car can read them and know there are sensors there, but it won't know which corner the sensor is located.
If we had access to the information as to which tire was reporting a low pressure condition like you can see via the IDS machine allegedly according to the service manual it would be extremely useful to know which corner was which. Hence why there is a triggering tool to let the car learn which sensor is at which corner.
This is not necessary if all you want is the idiot light to come on when the tires are low however as yes they do get read by the car regardless of position assuming the initial conditions for sensor engagement are met.