DPF Off — disabling the diesel particulate filter in the ECU

DPF Off disables the diesel particulate filter in the ECU software. The unit stops estimating soot, stops requesting regenerations and stops monitoring the filter, so DPF faults, the warning light and filter-related power limits go away. The option is meant for cars where the filter has been removed or emptied. Send us the original file and get a ready-to-flash file with corrected checksums, on average in 30–60 minutes.

How a diesel particulate filter is built

The DPF (PSA calls it FAP) sits in the exhaust after the diesel oxidation catalyst (DOC), often in the same housing. Inside is a ceramic block with long parallel channels, usually silicon carbide on passenger cars. Every other channel is plugged: inlet channels are open at the front and blind at the back, outlet channels the other way round. The gas can only get out by passing through the porous wall, and the soot stays on it.

Around the filter there are exhaust temperature sensors and a differential pressure sensor. Its two pipes are connected before and after the filter: the more soot in the channels, the higher the pressure drop at the same gas flow. The ECU uses these signals to decide when the filter needs cleaning.

Regeneration: how the soot is burned off

Burning the soot out of the filter is what regeneration means. With oxygen, soot burns quickly and completely only at around 550–600 °C. With nitrogen dioxide (NO₂) the reaction starts at roughly 250 °C, so on long drives under load part of the soot burns by itself: the catalyst turns some NO into NO₂, which oxidises the soot. This is passive regeneration. VW mounts its platinum-coated filter close to the engine, and on the motorway the gas in it reaches 350–500 °C.

In town the exhaust is too cold for that, so the ECU steps in. This is active regeneration:

On a VW 2.0 TDI with unit injectors it works like this: the ECU shuts the EGR, follows a reduced main injection with a late injection at about 35° after TDC, closes the throttle partly and adjusts boost so the driver feels no drop in pull. The gas heats up to 600–650 °C, and the regeneration lasts about 10 minutes. According to the Land Rover owner handbook, it happens roughly every 300–900 km and takes 10–20 minutes of steady driving at 60–112 km/h. If the trip ends sooner, regeneration is interrupted and the ECU tries again next time.

How the ECU decides the filter needs cleaning

The ECU estimates filter load in two ways. A calculation model works out how much soot the engine has produced at the load points it has been driven at. The measurement uses the pressure sensor: from the pressure drop and the gas flow the ECU works out how much soot is already sitting in the channels. Once the load reaches a threshold, regeneration starts. On a VW you can see all of this in the scan tool: "soot mass calculated", "soot mass measured", "oil ash volume" and the distance since the last regeneration.

Example thresholds: VW 2.0 TDI, model years 2009–2013, Tech Tip TT 26-11-01. Other engines and ECUs use their own values.

The upper limit is there for a reason: VW warns that regenerating a heavily loaded filter can overheat and damage it. The same bulletin has another condition that is easy to miss: with a stored fault for an exhaust temperature sensor, the mass air flow sensor or the differential pressure sensor, the system will not run a regeneration at all. On the earlier unit-injector TDIs a failed sensor made the ECU fall back to regenerating by distance or engine hours, and VW says plainly that this does not work for long. Soot keeps building up in the meantime.

Why a DPF gets blocked

• Short trips. Regeneration has no time to finish, the next one starts from a higher load, and soot builds up faster than it burns. When the filter light comes on, VW asks for about 15 minutes of steady driving above 60 km/h, in 4th or 5th gear at around 2000 rpm.
• The engine makes more soot than it should. A boost leak (VW notes it makes the soot load rise rapidly), dribbling injectors, an EGR valve stuck open, a dirty air filter, a turbo pushing oil.
• A sensor fault. A faulty temperature sensor, pressure sensor or MAF blocks regeneration. The pressure sensor pipes clog with soot condensate, and the ECU sees a wrong pressure drop.
• Ash. Engine oil additives leave incombustible ash when the oil burns. Regeneration does not remove it: ash collects at the blind ends of the channels and takes up more volume as the mileage grows. Hence the need for low-ash oils (ACEA C) and the link between oil consumption and filter life.

The symptoms are familiar: regenerations come more and more often (the ECU may store P2459), fuel consumption goes up, the engine pulls worse, the DPF light comes on, and with a heavily loaded filter the ECU limits power. Frequent regenerations are bad for the oil too: with late injection some fuel lands on the cylinder walls and drains into the sump. A service regeneration with a scan tool helps while the filter is full of soot. It does nothing about ash, and such a filter has to come off for cleaning or be replaced.

DPF fault codes

Typical codes per SAE J2012. VAG, PSA, Ford and other makes also use their own codes for the same faults.

If the filter is removed and the software is left as it was, the pressure drop falls almost to zero. That usually brings up P244A and P2002, the warning light comes on, and the engine may go into limp mode.

What changes in the software

Clearing the faults after removing the filter does not work: the ECU compares the pressure drop with the gas flow on every drive and finds the missing filter again. So DPF Off changes the logic in the file itself.

Checksums are recalculated, so the file is ready to flash straight away. We do DPF Off for diesel ECUs from Bosch (EDC and MD), Siemens/Continental (SID), Delphi, Denso, Marelli and others. EGR Off, AdBlue Off and Stage 1 can go into the same file. If the filter works with an additive (FAP on PSA engines and cars that use them), add EOLYS/ADDITIVE OFF.

What to do with the filter and sensors

DPF Off does not cure a blocked filter that stays in the exhaust. With no regeneration the ceramic will clog with soot for good: back pressure rises and the engine loses pull. So the option is ordered when the filter has been removed, replaced with a pipe, or the ceramic taken out of the housing.

• The oxidation catalyst is worth keeping if you can. It burns off CO and hydrocarbons, and without it the exhaust smells stronger.
• Temperature sensors stay in and plugged in: on many ECUs they protect the turbo and the catalyst from overheating, and a fault on them will light up the dash.
• The differential pressure sensor and its pipes stay in place unless agreed otherwise for your ECU: on some software its signal is used for more than the filter. We will advise in the order.
• Check the oil after frequent regenerations. If it smells of diesel or the level has crept up, change it.
• Find the cause of the soot before flashing. If injectors, a boost leak or the EGR clogged the filter, the engine will smoke without it, and the file will not fix that.

How to order the file

1. Read the original file via OBD or on the bench with the tool you use. We need an unmodified stock file.
2. Upload it to the portal and select DPF OFF. You can add EGR OFF, EOLYS/ADDITIVE OFF or Stage 1 at the same time.
3. Get the finished file with recalculated checksums, on average within 30–60 minutes.
4. Flash the file, clear the faults and check after a drive that no DPF faults come back.

Keep the original file: with it the car can go back to stock if a working filter is fitted again. If your ECU is not in the list below, send the file with a request and we will check whether there is a solution.

Without a particulate filter a diesel emits many times more particles. In the EU, the UK, the US and a number of other countries this is prohibited on public roads and may cause an inspection failure: in the UK a car without its factory-fitted filter has automatically failed the MOT since 2014, and in Germany Euro 6 diesels have had a particle count test at the periodic inspection since July 2023. The service is intended for tuners and is used where the law allows it: motorsport, off-road, export, vehicles not used on public roads. Responsibility for using the file lies with the vehicle owner.