Differential Pressure Sensor
WARNING: This page is about a different car, the 2019 Jaguar XF. However, it is still accessible from the selected car via links, so may be relevant.
As the amount of particulates trapped by the DPF increases, the pressure at the inlet side of the DPF increases in comparison to the DPF outlet. The DPF software uses this comparison, in conjunction with other data, to calculate the accumulated amount of trapped particulates.
By measuring the pressure difference between the DPF inlet and outlet and the DPF temperature, the DPF software can determine if the DPF is becoming blocked and requires regeneration.