Will P2002 fail an MOT?

Yes, and by several separate routes. The illuminated engine management lamp is a major defect on diesels first used on or after 1 July 2008. A diesel fitted with a particulate filter also fails if the exhaust emits visible smoke of any colour, and fails if it exceeds the smoke opacity limit during the metered acceleration test. Most seriously, if the tester finds the filter has been removed or the casing cut open and rewelded, the car fails outright — testers are specifically instructed to look for evidence of that.

Does P2002 always mean the DPF needs replacing?

No, and it should never be assumed. The control unit judges the filter through a differential pressure sensor and two small sensing pipes, and a faulty sensor, a soot-blocked pipe, a split hose or pipes reconnected the wrong way round after earlier work will all produce this code with the filter in perfectly good order. Checking that the sensor reports essentially no pressure difference with the engine off is quick, and it is the correct first step before authorising one of the most expensive exhaust components on the car.

Can I drive with a P2002 code?

Short journeys are usually possible, though some cars restrict power in response. It is not one to sit on. If the filter substrate has broken up, debris can travel down the exhaust and restrict it, and the cause is often something that is actively harming the engine — repeatedly interrupted regenerations put diesel into the sump, which thins the oil. Check the oil level and if it is rising above the full mark, stop driving it and get it looked at.

Can an MOT tester tell if the DPF has been removed?

Yes, and they are required to look. Since 2014 the inspection includes a visual check of the particulate filter, and a tester who finds the canister has been cut open and rewelded, or that the filter is simply absent where one was fitted as original equipment, fails the vehicle. The stored fault code is not what they act on — the physical evidence is. Anyone buying a used diesel is inheriting that risk, so a look underneath before purchase is worth the effort.

Powertrain code · standard

P2002Diesel particulate filter not trapping soot properly

Standard definition: Diesel Particulate Filter Efficiency Below Threshold (Bank 1)

Last updated 27 July 2026

Quick answer

The control unit has concluded the particulate filter is no longer doing its job. That can mean the filter has broken up internally, but it can equally mean the pressure sensor watching it is lying — and on a car bought second-hand it can mean the filter was removed before you owned it, which is an outright MOT failure.

How the car works this out

The control unit judges the filter mainly from the pressure difference between the exhaust before it and after it, measured by a differential pressure sensor plumbed in with two small pipes, and interpreted alongside exhaust flow and temperature. A filter doing its job creates a predictable restriction that rises as it fills with soot and falls again after a regeneration. If the pressure difference is far too low for the flow passing through, the filter is not trapping anything — the substrate has cracked, melted or been removed. If the calculated efficiency sits outside its expected range in either direction, this code is stored.

What you might notice

Frequently nothing to feel, which is what makes the removed-filter case so easy to miss
Visible smoke from the exhaust, particularly under acceleration
A particulate filter warning lamp alongside the engine management lamp
Reduced power, if the car has responded by restricting the engine
A rattle from the filter housing if the substrate has broken up

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1The filter substrate cracked or melted, typically after a series of regenerations that ran too hot or were repeatedly interruptedCommon
How to check: A rattle when the housing is tapped, or loose material audible inside, indicates a broken substrate.
2A faulty differential pressure sensor, or its sensing pipes blocked with soot, split or fitted the wrong way roundCommon
How to check: With the engine off the sensor should report essentially no pressure difference. Anything materially away from zero at rest condemns the sensor or its plumbing rather than the filter, and this is much the cheaper outcome.
3The filter has been removed or hollowed out by a previous owner and the casing reweldedCommon
How to check: Look underneath for a cut and rewelded seam in the filter casing. This is exactly what an MOT tester is instructed to look for, so finding it yourself first is worth doing before booking a test.
4An exhaust leak between the filter and the points where the pressure pipes are tapped inPossible
5A poor quality or incorrect replacement filter with too little substrate to work properlyPossible
6A genuinely blocked filter, loaded with ash rather than sootPossible

What to do about it

1Have the differential pressure sensor and its pipes checked before anything else. It is by far the cheapest thing on the list, it is a common cause, and a filter should never be replaced without ruling it out.
2Get the car up and inspect the filter casing for a cut and rewelded seam, particularly if you bought it used. Knowing before the MOT rather than after is a great deal less painful.
3Ask why, if the filter really has broken up. Repeated interrupted regenerations, a leaking injector or an engine burning oil will destroy a replacement in the same way.
4Check the oil level and condition. Interrupted regenerations put diesel into the sump, and an oil level rising above full is its own engine-destroying problem.
5Do not accept removal as a solution. It fails the MOT permanently and cannot be undone without buying the filter back.

Can you keep driving?

Briefly, gently

The car will usually drive, though some vehicles restrict power in response. The reasons to keep it short are that a broken substrate can migrate down the exhaust and restrict it, that the underlying cause is often something actively damaging the engine such as fuel diluting the oil, and that if the filter genuinely is not trapping soot the car is putting out particulates it was designed not to.

Will it fail an MOT?

No emissions code has more ways to fail an MOT than this one. First, the lamp: a major defect on diesels first used on or after 1 July 2008. Second, visible smoke — a diesel fitted with a particulate filter fails if the exhaust emits visible smoke of any colour, and a filter that has stopped trapping soot is precisely the thing that produces it. Third, the smoke opacity limits measured during the metered acceleration test. Fourth and most serious, tampering: if the tester finds the filter has been removed, or the casing cut open and rewelded, the car fails outright, and they are specifically instructed to look for it. That last route is worth emphasising for anyone who has bought a diesel second-hand, because you can inherit the failure without ever having made the decision.

The light this turns on

Diesel particulate filter lightThe diesel particulate filter has collected more soot than it can hold and needs to burn it off. Caught early this is fixed by a longer, faster drive; ignored, it turns into a blocked filter costing four figures.

Common questions

Will P2002 fail an MOT?: Yes, and by several separate routes. The illuminated engine management lamp is a major defect on diesels first used on or after 1 July 2008. A diesel fitted with a particulate filter also fails if the exhaust emits visible smoke of any colour, and fails if it exceeds the smoke opacity limit during the metered acceleration test. Most seriously, if the tester finds the filter has been removed or the casing cut open and rewelded, the car fails outright — testers are specifically instructed to look for evidence of that.
Does P2002 always mean the DPF needs replacing?: No, and it should never be assumed. The control unit judges the filter through a differential pressure sensor and two small sensing pipes, and a faulty sensor, a soot-blocked pipe, a split hose or pipes reconnected the wrong way round after earlier work will all produce this code with the filter in perfectly good order. Checking that the sensor reports essentially no pressure difference with the engine off is quick, and it is the correct first step before authorising one of the most expensive exhaust components on the car.
Can I drive with a P2002 code?: Short journeys are usually possible, though some cars restrict power in response. It is not one to sit on. If the filter substrate has broken up, debris can travel down the exhaust and restrict it, and the cause is often something that is actively harming the engine — repeatedly interrupted regenerations put diesel into the sump, which thins the oil. Check the oil level and if it is rising above the full mark, stop driving it and get it looked at.
Can an MOT tester tell if the DPF has been removed?: Yes, and they are required to look. Since 2014 the inspection includes a visual check of the particulate filter, and a tester who finds the canister has been cut open and rewelded, or that the filter is simply absent where one was fitted as original equipment, fails the vehicle. The stored fault code is not what they act on — the physical evidence is. Anyone buying a used diesel is inheriting that risk, so a look underneath before purchase is worth the effort.

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