DPF fault codes P2463, P2002, P242F, P2453 explained

What does a DPF fault code mean? It tells you which of the engine computer’s checks on the diesel particulate filter (DPF) has failed: too much soot (P2463), too much ash (P242F), a filter that no longer catches enough soot (P2002), or a pressure reading that doesn’t add up (P2452 to P2455, P244A and P244B). BM Catalysts, who make every part we sell, say these codes are rarely caused by a faulty DPF¹. Most point to something that stops the filter working, and several point to a sensor or a pipe that costs far less than a filter.

Below is what each code means, what a garage should check before anything is replaced, and when the answer really is a new filter. How a DPF cleans itself is covered in what is a DPF and how regeneration works; this guide starts where the warning light ends, with the code. On many Renault and Dacia models a particle filter fault shows as the message “Check anti-pollution system”: see what it means and what to do.

The codes at a glance

Code	What it means	Check first
P2463	Too much soot in the filter	Why regeneration isn’t finishing; the pressure sensor
P242F	Too much ash in the filter	The pressure sensor and its hoses; then the ash itself
P2002	The filter isn’t catching enough soot	A cracked or failed filter; the pressure sensor
P2452 to P2455	A fault in the pressure sensor’s circuit	The sensor, its wiring and connector, its hoses
P244A, P244B	Pressure across the filter too low or too high	Exhaust leaks near the sensor; leaking or blocked hoses
P2458, P2459	Regeneration too long or too frequent	Why regeneration isn’t working normally

Where the codes come from

A diesel’s on-board diagnostic (OBD) system keeps watch on the DPF. Type-approval law requires it to detect a particulate filter that has failed or been removed, and to record each fault with a standard code from ISO 15031-6 or SAE J2012, two technically equivalent standards^2,3. The codes must be readable with standard diagnostic equipment², so a code reader and a dealer’s equipment show the same P2463.

A code is where a diagnosis starts, not where it ends. In BM Catalysts’ words, a fault code “will not tell you which exact part of the vehicle requires fixing or replacing”, only what needs to be tested¹.

• Two extra characters? Some scan tools show a code as P2463-00 or P245800. The extra two characters are a “failure type”, a sub-code defined in the same standard³, and manufacturers print codes that way in their own bulletins⁴. Look up the first five characters.
• Code not listed here? It may be one of the manufacturer’s own codes, which the law allows where no standard code fits². On Euro 5 and Euro 6 Fords and on several Peugeot, Citroën and Fiat vans, P244C and P246B are typical when the fuel vaporiser fails: see our DPF fitting notes. P0420 is a catalytic converter code, covered in what causes a faulty catalytic converter.

P2463: soot accumulation

The standard description is “Diesel Particulate Filter Restriction – Soot Accumulation”^1,4. The engine computer has detected, usually from the exhaust pressure, that the filter holds more soot than its limit allows¹. In plain terms, regeneration (the process that burns the soot off) hasn’t been finishing.

BM treats it as a priority, because a restricted DPF can damage the engine or the fuel system. Before the filter is blamed, it lists these causes to rule out¹:

• soot building up because regeneration isn’t happening often enough;
• a faulty DPF pressure sensor or exhaust pressure sensor;
• open or short circuits in the wiring to the exhaust pressure sensor or the DPF injection system;
• on vehicles that use AdBlue (diesel exhaust fluid), too little of it or the wrong fluid.

A soot code isn’t always soot. Chrysler’s bulletin for P2463 and the pressure-sensor codes P2453 to P2455 on one of its diesels is a repair of the pressure sensor’s connector, where the corrosion is hard to see: “normal inspection methods may not uncover” it⁵.

How full the filter is decides the fix: a sustained drive, a forced regeneration at a garage, or a new filter once it is too full to regenerate (regeneration explained). Whichever it is, find out why regeneration stopped first. The usual reasons are in blocked DPF? The causes to fix before replacing it.

P242F: ash accumulation

The standard description is “Diesel Particulate Filter Restriction – Ash Accumulation”^1,4. Ash is what is left after the soot has burnt. It comes mainly from additives in the engine oil, plus fuel and engine wear, and regeneration doesn’t remove it⁶. So ash builds up over the whole life of the filter and is an important limit on how long it lasts⁶. P242F means the engine computer has decided the ash level is now restrictive¹.

BM’s list of causes to rule out before assuming the DPF is at fault¹:

• a defective DPF pressure sensor, or clogged sensors or hoses;
• an open or short circuit in the pressure sensor’s wiring;
• regeneration not working efficiently;
• overuse of engine or fuel additives;
• and the ash itself.

If the ash load is real, no regeneration will clear it, because ash doesn’t burn: the filter has to be cleaned of ash or replaced⁶. If a cleaning involves cutting the DPF open, keep the paperwork for the MOT⁷ (why, in DPF removal and the law). A new filter starts with no ash; after it is fitted, the engine computer must be reset and a forced regeneration run¹. The steps are in how to replace a DPF.

P2002: the filter isn’t catching enough soot

Recent manufacturer bulletins describe it as “Diesel Particulate Filter Efficiency Below Threshold”⁴; older ones as “Particulate Trap Bank 1 Efficiency Below Threshold”⁸. On General Motors diesels, for example, it sets when the system detects “a cracked or broken DPF”⁹.

A sensor can set it too. Audi found that moisture getting into the differential pressure sensor on some Q7 TDIs could log P2002 as well as the pressure-sensor codes, and the fix was a new sensor⁸.

To confirm that the filter itself has failed, General Motors tells its technicians to hold a cloth across the tailpipe while the engine is revved, though not straight after a regeneration, when even a good filter lets more through. Soot on the cloth means the filter is “no longer able to capture all of the soot particles” and needs replacing; no soot, or very little, means it doesn’t⁹. A filter that lets soot through also fails the MOT⁷: see failed your MOT on emissions?

P2452 to P2455, P244A and P244B: the pressure sensor and its hoses

The DPF pressure sensor measures the exhaust pressure across the filter through small pipes and hoses, and the engine computer uses the reading to judge how much the filter is holding back¹. When the reading is missing, implausible or out of range, you get one of these codes:

Code	Description in manufacturers’ documents
P2452	DPF pressure sensor circuit1,8
P2453	DPF pressure sensor circuit range/performance1,8
P2454	DPF pressure sensor circuit low5,8
P2455	DPF pressure sensor circuit high5
P244A	DPF differential pressure too low1
P244B	DPF differential pressure too high1

For P2452 and P2453, BM lists among the causes clogged pressure sensors or hoses, a faulty sensor, open or short circuits in its wiring and inefficient regeneration. For P244A and P244B it lists exhaust leaks before or near the pressure sensor, leaks in the sensor’s connecting hose, and aftermarket or performance modifications¹. P244A matters more than it looks: the engine computer reads the low pressure as a filter that isn’t there and switches active regeneration off¹. General Motors says it sets when the sensor lines are “disconnected or blocked”⁹.

Manufacturers have fixed these codes with a new sensor⁸, or a new connector, terminals and sensor⁵. On the Chrysler in that bulletin, the sensor’s stored offset value must also be reset whenever the sensor is replaced or a hose repaired⁵. BM’s fitting advice is to check that the pressure pipes are free from blockages and the rubber hoses aren’t worn, and to use new ones where needed¹⁰.

Pipes cost far less than a filter. Our DPF pressure pipes cost £33.99 to £117.99 including VAT, against £120.99 to £795.99 for a DPF on its own (prices on 13 October 2026). More on filter prices in how much does a replacement catalytic converter or DPF cost?

P2458 and P2459: regeneration taking too long or happening too often

P2458 is “Diesel Particulate Filter Regeneration Duration”¹¹ and P2459 is “Diesel Particulate Filter Regeneration Too Frequent”¹². The engine computer keeps track of its regenerations, and these codes mean they are taking longer, or coming round more often, than they should. Ram warns that on its trucks, P2459 left set for a long time puts the engine into reduced power¹².

Manufacturers sometimes issue a fix for these codes on particular models. For P2458 on some of its diesels, Volkswagen’s fix was a software update¹¹; for P2459 on certain Ram trucks, it was a new DPF¹². A dealer can tell you whether one applies to your vehicle. Otherwise, work through the reasons regeneration fails.

Does a DPF fault code mean I need a new DPF?

Usually not as the first step: BM says these codes are rarely caused by a defective DPF¹. The filter itself is the likely answer when:

• the ash load is genuinely full (P242F, once the sensor and hoses have been checked)⁶;
• the filter is confirmed cracked or failed (P2002 with soot at the tailpipe)⁹;
• it is too full of soot to regenerate (P2463 that a forced regeneration can’t clear)¹⁰.

Even then, fix whatever stopped the old filter working, or the new one will go the same way. And if a code comes back after a new DPF has been fitted, look elsewhere: BM says a newly fitted DPF “should never be the cause of a fault code”¹.

DPF fault codes and the MOT

If the code has turned the engine management light on, a diesel first used on or after 1 July 2008 will fail its MOT: a light showing a malfunction is a major defect⁷. The MOT’s other DPF checks (smoke, and a filter that has been removed or tampered with) are covered in failed your MOT on emissions? and is DPF removal legal in the UK?

Find the part

If the diagnosis points to the filter or its pipes, browse DPFs, combined catalytic converter and DPF units and DPF pressure pipes, or go straight to your vehicle: Ford Transit, Ford Kuga, Nissan Qashqai, Vauxhall Vivaro, Peugeot 308, Citroen C4, Volkswagen Golf, Audi A3 or Mercedes Sprinter. For any other vehicle, use the part finder below.

Frequently asked questions

What does P246300 or P245800 mean?

The same as P2463 (soot accumulation) and P2458 (regeneration duration). The last two characters are a failure type, a sub-code that some scan tools show³.

Can I clear a DPF fault code myself?

A code reader can clear it, but clearing the code doesn’t clear the fault: if the fault is still there, the engine computer will detect it and log the code again. The system itself may only erase a stored code once the same fault hasn’t been logged again for at least 40 engine warm-ups or driving cycles². After a new DPF is fitted, though, clearing all fault codes is part of the job¹ (see how to replace a DPF).

Will a DPF fault put my vehicle into limp mode?

It can. A filter left to block will eventually send the vehicle into limp mode to protect the engine¹⁰, and on Ram’s trucks, P2459 left for a long time causes reduced power¹². The stages are explained in what is a DPF and how regeneration works.

Is P0420 a DPF code?

No. P0420 means “catalyst system efficiency below threshold”, a catalytic converter code¹. See the P0420 code explained.