The exhaust gas pressure sensor is measuring the difference in air pressure before and after the air passes the particle filter.

The difference in air pressure rises as the particle filter soils more and more.

At some point the particle filter is too clogged to function properly so the engine-management starts the regeneration process.

The most common reasons for a defect of the exhaust-gas-pressure-sensor are pollution, corrosion or damaged cables.

If the exhaust gas pressure sensor is broken it will not send the correct signals to the engine-management system. The board computer will signal an error code and the regeneration process of the diesel filter will not work properly.