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P2455 – Diesel Particulate Filter Pressure Sensor A Circuit High (OBD2)

P2455 means "Diesel Particulate Filter Pressure Sensor A Circuit High". The voltage in the diesel particulate filter / NOx adsorber circuit is above the permitted maximum. For most sensors this points to an open signal or ground wire – the signal "floats" up to the reference voltage – or to a short to voltage.

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P2455 quick summary

Fault codeP2455
MeaningDiesel Particulate Filter Pressure Sensor A Circuit High
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityMedium
Can I drive?Yes, but have it checked. A cracked filter or faulty sensor can lead to further DPF problems and a failed inspection.
Repair cost€30 – €2,500

How the diesel particulate filter and NOx adsorber work

The diesel particulate filter traps soot and the NOx storage catalyst stores nitrogen oxides; these codes mean the control unit judges their efficiency to be below the legal limit.

The DPF is a ceramic filter that traps soot. A differential pressure sensor measures the pressure drop across it; when the filter is full, the control unit raises the exhaust temperature to burn the soot off (regeneration). P2002 does not mean the filter is blocked – it means the pressure difference is too LOW, so the control unit thinks the filter is not filtering well enough, for example because it is cracked, missing, or because the sensor or its hoses are faulty.

Some diesels use a NOx storage catalyst (NOx adsorber, lean NOx trap) that stores NOx and is cleaned periodically by running the engine briefly rich. P2000 means its storage efficiency is below the limit, usually because it is aged, poisoned by sulphur, or because the NOx sensors are faulty.

Both systems are required for the vehicle's type approval. Removing or disabling them is illegal and makes the car fail inspection.

Symptoms of P2455

  • Check Engine light on
  • Often no noticeable power loss
  • Black soot in the tailpipe (cracked DPF)
  • Regenerations not running or running too often
  • Failed emissions inspection

Most common causes of P2455 (most likely first)

Mechanic's Pro Tip

Before replacing a DPF for P2002, replace the hoses to the differential pressure sensor and compare the sensor reading with a known-good sensor. A cracked rubber hose costs a few euros; a DPF costs a four-figure sum.

  1. 1.Open circuit in the signal or ground wire

    Most likely

    A loose ground connection is a very common cause.

  2. 2.Signal wire shorted to the 5 V reference or battery voltage

  3. 3.Faulty diesel particulate filter / NOx adsorber

  4. 4.Cracked, swapped or disconnected sensor hoses

  5. 5.Cracked or melted DPF substrate

  6. 6.Aged or sulphur-poisoned NOx storage catalyst (P2000)

Step-by-step diagnostic guide

  1. 1

    Read codes and DPF values

    Read all codes and check soot load, ash load and differential pressure in live data.

  2. 2

    Check signal and ground

    With the ignition on and the diesel particulate filter / NOx adsorber plugged in, back-probe the signal and ground wires. A signal stuck at reference or battery voltage points to an open ground/signal wire or a short to voltage.

    Multimeter: Ground wire to battery negative: below about 0.1 V. Signal stuck at about 5 V (or 12 V) = open or short to voltage.

  3. 3

    Check the differential pressure

    With the engine off, the differential pressure should read about zero. At idle it should be a few mbar and rise clearly with engine speed.

    Multimeter: A value stuck near 0 mbar while revving points to the sensor or its hoses.

  4. 4

    Inspect sensor hoses

    Check both hoses for cracks, blockages, loose fittings and correct routing (upstream/downstream not swapped).

  5. 5

    Check for soot behind the DPF

    Soot in the tailpipe after the filter points to a cracked DPF.

  6. 6

    Check NOx sensors and catalyst (P2000)

    Compare NOx sensor readings and run any regeneration or desulphurisation routine before condemning the catalyst.

Frequently asked questions

Can I keep driving with P2455?

Yes, but have it checked. A cracked filter or faulty sensor can lead to further DPF problems and a failed inspection.

How much does it cost to fix P2455?

Typical repair costs are 30 € – 2500 €, depending on the cause and the vehicle. The most common fixes are: open circuit in the signal or ground wire; signal wire shorted to the 5 V reference or battery voltage; faulty diesel particulate filter / NOx adsorber. Always confirm the cause with the tests above before buying parts.

Does P2002 mean my DPF is blocked?

No. A blocked filter usually sets P2463 or high soot-load codes. P2002 means the filter appears to filter too little, often because of a sensor or hose fault or a cracked filter.

Can I remove the DPF?

No. Removing it is illegal for road vehicles in the EU and leads to a failed inspection and possible fines.

What is the difference between P2455 and similar codes?

P2455 belongs to a group of codes for the same component that differ in the type or location of the fault: P2452 – Diesel Particulate Filter Pressure Sensor A Circuit; P2453 – Diesel Particulate Filter Pressure Sensor A Range/Performance; P2454 – Diesel Particulate Filter Pressure Sensor A Circuit Low; P2458 – Diesel Particulate Filter Regeneration Duration; P2459 – Diesel Particulate Filter Regeneration Frequency; P2463 – Diesel Particulate Filter Restriction - Soot Accumulation. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.