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SHR AUTOSENSOR · TECHNICAL NOTES

A DPF pressure fault does not always mean a failed sensor

The sensor compares pressure at two points around the filter. A blocked or split hose, a plugged port or a wiring fault can produce a similar complaint.

What it measures

A differential-pressure sensor receives pressure from the exhaust path before and after the DPF and reports the difference to the engine controller. The controller uses that signal as one input when assessing filter restriction and regeneration conditions. The exact pressure range, signal and threshold depend on the vehicle and sensor calibration.

DPF differential-pressure measurement schematicExhaust flows through a particulate filter; two pressure tubes connect the upstream and downstream sides to a sensor.Exhaust inletDPFPressure sensortwo pressure portsupstream / downstream pressure lines
Schematic only. Hose routing, port position and sensor design vary by vehicle.

Checks to make before condemning the sensor

  1. Read the vehicle-specific diagnostic procedure and freeze-frame/live data. A code identifies a circuit or plausibility condition; it does not by itself prove the sensor has failed.
  2. Inspect both pressure tubes and exhaust take-off ports for cracks, leaks, heat damage, blockage or condensation. Check routing against the service information.
  3. Check connector locking, terminal condition, supply, ground and signal wiring. Do not back-probe or apply pressure outside the manufacturer's test method.
  4. Compare readings with the engine off and under the operating conditions specified by the maker. Do not use a universal pressure threshold across different engines.
  5. After repair or replacement, perform only the relearn/adaptation required by the vehicle procedure and confirm the result with a controlled road test.

Walker describes differential-pressure sensors as monitoring pressure on both sides of the DPF. Bosch also lists differential-pressure sensing within its exhaust-treatment portfolio. Both sources support the system role; vehicle-specific test values still come from the service manual.

Walker Products: Differential Pressure Sensors · Bosch Aftermarket: Sensors