Durite de pression différentielle obstruée ou fendue

One of the pair of hoses connecting the differential pressure sensor across the particulate filter, blocked or split. The sensor measures the difference between two points, so a fault in either hose corrupts the reading even though the sensor is perfect.

The direction of the error decides which expensive mistake follows. A blocked hose freezes one side of the measurement, so the reported difference stops tracking the filter's real state — the module either never regenerates and lets the filter block, or regenerates constantly and dilutes the oil. A split hose reduces the measured difference, so a genuinely loaded filter reads clear.

These are the most-failed part of the whole system because they are small-bore lines carrying sooty exhaust and running through the hottest part of the underbody. They soot up internally, harden, and split at the fittings. Disconnect and blow through both before condemning the sensor or the filter, and compare the pressure reading at idle against zero — a difference at idle that is not near zero indicates a hose fault rather than a loaded filter.