DPF differential pressure sensor
Definition
The differential pressure sensor measures the pressure drop across the DPF through two hoses connected before and after the filter; the ECU uses this value, together with exhaust flow and temperature, to estimate soot load and decide when to regenerate. At idle with a clean filter the reading is a few millibars, rising to 100-200 mbar under load as soot builds; with the engine off it must read zero, and a sensor that does not is drifted. Failures are cracked or blocked hoses (soot, condensation freezing), a drifted sensor that over-reports soot and triggers constant regenerations or under-reports and lets the filter overfill, and corroded connectors. Always check and clear the hoses before condemning the sensor, and perform a soot-mass reset only when the sensor has been replaced or the filter cleaned. Codes: P2452-P2455 (sensor circuit, range, low, high), P2456 (intermittent), P2002 (DPF efficiency), P2463 (soot accumulation), P0470-P0473 (exhaust pressure sensor), P24A4/P24A5 (DPF restriction).