Reservoir Blockage
WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2015 Jaguar XKR-S, 2015 Jaguar XKR, 2015 Jaguar XK, 2014 Jaguar XKR-S, and 2014 Jaguar XKR. However, it is still accessible from the selected car via links, so may be relevant.
Remove reservoir cap and (using a mirror) visually inspect the power steering fluid reservoir filter for signs of blockage. It is normal that a small amount of debris could be on the filter.
The filter mesh should not be more than 30% blocked (as in left-hand picture below), if the mesh is more than 30% blocked (as in the right-hand picture below), the power steering system fluid reservoir should be replaced.