Short answer

The main DPF sensor is the differential pressure sensor, which measures the pressure difference across the filter so the ECU can estimate soot load. Exhaust temperature sensors control regeneration. A faulty sensor or split sensor hose can cause warning lights and failed regenerations even when the filter itself is fine.

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The differential pressure sensor

Also called the DPF pressure sensor or exhaust back pressure sensor, it is connected by two small pipes or hoses to the exhaust before and after the filter. As soot builds up, the pressure difference rises. The ECU uses this reading, together with its own soot model, to decide when to regenerate and to detect a blocked filter.

The hoses run close to hot exhaust parts and can crack, split, come off or block. A leaking hose reads low and a blocked hose can read high, so hose condition is one of the first things to check.

Exhaust temperature sensors

Temperature sensors before the oxidation catalyst and around the DPF let the ECU control regeneration temperature and protect the filter from overheating. If a temperature sensor fails, the ECU may stop regenerating altogether.

Particulate matter sensors

Some newer vehicles also have a particulate (PM) sensor after the DPF to check that the filter is working. It can detect a cracked or failed filter.

Testing and replacing DPF sensors

A technician compares live sensor readings with expected values at idle and under load, checks the hoses and connectors and, where needed, replaces the sensor and runs any adaptation the manufacturer requires. For sensor parts, see DPF sensors; for test equipment, DPF diagnostic tools.

Symptoms

  • DPF light on with a clean filter

    The ECU believes the filter is loaded when it is not.

  • Regeneration not starting

    Implausible readings stop the ECU from regenerating.

  • Frequent regenerations

    A sensor reading high triggers unnecessary regenerations.

  • Pressure-sensor fault codes

    Circuit or range/performance codes.

Common DPF fault codes

Code Meaning Typical next step
P2452 DPF pressure sensor A circuit Check wiring, connector and sensor.
P2453 DPF pressure sensor A circuit range/performance Check hoses for splits or blockages, then the sensor.
P244A DPF differential pressure too low Check for a disconnected or split hose, or a cracked filter.

Generic OBD-II codes. Manufacturers also use their own codes; always confirm with a scan tool and the vehicle's service information.