Are you sure tour car has tyre pressure sensors Craig ?
There are two different ways in which car tyre pressures are monitored.
The first, and most expensive is to have an individual pressure sensor in the valve of each tyre. If you have this type of system, you will be able to view the pressure for each individual tyre from the onboard computer. As one would expect, if any of the pressures are above, or below a certain threshold, then you will be alerted to the anomaly.
The second, and much more common method (although I haven’t checked fords preferred solution) doesn’t measure any pressures, but rather monitors the rotation of each wheel, taken from the ABS sensors. Once set, the car’s computer relates vehicle speed to wheel RPM, which, if all tyres are at the same pressure, will the same for each wheel. If there is a significant difference between the calculated (expected) wheel RPM for any of the 4 wheels, then this will trigger an alert. The system doesn’t act immediately to prevent false triggers such as wheelspin, pot-holes and of course turning around corners. Again, this system is now by far the most common, mainly because apart from the relevan software, it has no cost associated with it, as it is using mechanical and electrical components which are already in place.
If you’ve checked that all of your tyre pressures are OK, then other probable causes could be a dirty or faulty ABS sensor, or a heavy build up of dirt around whichever rortating part of your wheel/hub assembly is fitted with the castellations which the sensor counts as the wheel rotates.
Or it may just be that now the colder mornings are here, the system was previously reset with higher pressure values, i.e. when it was warmer. For this reason, such warnings are quite common at this time of year when it starts to get colder.
I would check and adjust the tyre pressures and then reset the monitoring system first thing in the morning, preferably on a cold one, as this is when the pressures will be at their lowest.
Let us know how you get on,
Ic.