DPF Off / EGR Off
Everything explained

DPF Off — deleting the particulate filter

The DPF (Diesel Particulate Filter), known as the FAP in France, is an emissions device fitted to diesel engines since roughly 2000. It traps the fine particles produced by combustion. The catch: over time the filter clogs and has to regenerate — a process that burns fuel, cuts power and causes no end of faults.

Why delete the DPF?

• A blocked filter — it is saturated and can no longer regenerate. A replacement runs from 600 to 2,000 €. The software delete is often the cheaper route.
• Constant regenerations — every 150 to 300 km the engine burns the filter clean. Power drops, consumption rises, and fuel dilutes the oil.
• Track or export use — for vehicles that never see a public road.
• Cars without a catalytic converter — track builds where the DPF has already been physically removed.

EGR Off — disabling the EGR valve

EGR (Exhaust Gas Recirculation) feeds part of the exhaust gas back into the intake to cut NOx emissions. In practice those hot, soot-laden gases coat the intake, the intercooler and the valves — bringing gradual power loss and recurring faults.

Symptoms of a failing EGR

• Engine warning light with a P0400 to P0409 code
• Gradual power loss, especially at part throttle
• Fuel consumption creeping up for no obvious reason
• An intake black with soot when you take it apart
• Blue or black smoke on start-up

DPF Off and EGR Off — can you do both?

Yes, and on high-mileage diesels it is often the sensible choice. The two deletes are independent in the ECU map, but they complement each other where engine health is concerned.

What the deletion actually changes inside the ECU

People talk about “deleting the DPF” as though it were a checkbox. Inside a control unit it is a set of linked changes, and that is exactly where a clean file parts company with one that will hand the car back to you in six months.

On the DPF side

• The soot load model — the ECU continuously estimates the mass of particulates trapped, from engine speed, load and air flow. That model is what triggers regeneration, so it has to be neutralised, not merely capped.
• The differential pressure sensor — it measures the pressure drop across the filter. With no filter the drop falls to zero and the ECU reads that as a failed sensor. Its value has to be replaced with something plausible, not zeroed.
• The regeneration routines — post-injection, exhaust temperature management, intake throttle control during the heating phase.
• The counters and their fault codes — distance since last regeneration, number of aborted regenerations, ash thresholds.

On the EGR side

• The flow demand — the maps that command valve opening are taken to zero across the whole speed and load range.
• The control loop — the ECU constantly compares measured air flow with expected air flow. If demand drops to zero while the loop stays live, the gap raises a fault.
• Valve position feedback — on electrically actuated EGR valves the ECU checks that the valve moves when asked.
• The injection maps — without recirculated gas the cylinder fill changes. A file that does not recalibrate injected quantity and timing leaves the engine running hotter than before.

Which engines and ECUs are involved

The particulate filter reached European diesels in series production in the early 2000s — Peugeot introduced one on the 607 as early as 2000 — and became universal with Euro 5 in 2011. Any diesel newer than that has one. EGR is far older and is fitted to diesels and to many direct-injection petrol engines alike.

The generation matters more than the badge. On an EDC15 everything is fairly direct and the maps are barely protected. On an EDC17 there are more cross-linked strategies, several checksums, and often read protection that forces you to open the ECU rather than work through the diagnostic socket. On the newest generations, getting the read out at all is the main obstacle.

What it costs, next to the repair

This is almost always the real reason behind the question, so here are the numbers. A new original particulate filter runs €600 to €2,000 depending on the vehicle, fitted. Professional filter cleaning costs €150 to €350 and works as long as the filter is not saturated with ash — which it usually is beyond roughly 200,000 km. An EGR valve is €200 to €600 to replace, more if the EGR cooler is involved.

Against that, the software side is a matter of tens of euros. That ratio explains the demand — and it is also why the framing has to be honest: the saving is real, but it only applies to a vehicle that does not use public roads. On a car that has to pass its roadworthiness test, the real comparison is cleaning versus replacement.

Checksums: the step everyone forgets

A control unit verifies the integrity of its memory at start-up. Every modified area breaks the checksum covering it, and a file flashed without recalculation ends, at best, in a no-start — at worst in an ECU that no longer answers the diagnostic tool at all.

On Bosch EDC17 and MED17 there are several checksums in different places, plus a global check at start-up. Correcting them by hand without knowing which covers what is the fastest way to brick an ECU.

The four mistakes we see most often

• Doing the software delete with the filter still fitted. The ECU stops regenerating, the filter keeps filling, and it ends up completely blocked — this time with back pressure that damages the turbo. The correct order is always physical removal first, software second.
• Clearing fault codes without addressing the cause. Masking a P2002 while the soot model still runs only postpones the problem: the engine will drop into limp mode a few hundred kilometres later.
• Reusing a file found on a forum. Same model, same engine, different software version: the addresses no longer line up.
• Skipping recalibration. A closed EGR without an injection adjustment means more air, more torque — and more exhaust temperature. On a tired engine, that is what breaks it.

How to tell a clean job from a bad one

Three checks, all doable with a decent diagnostic tool, are enough to know whether the file holds:

• No fault codes after 200 km, with the memory cleared at the start. A code that returns after a few days points to a strategy that was missed.
• The distance-since-last-regeneration counter stops moving, or sits at a fixed value. If it is still climbing, the soot model is still running.
• Exhaust temperatures under load stay where they were. A marked rise after an EGR delete means the injection was never revisited.

What about Vmax Off?

Speed derestriction is a different kind of change: it touches no emissions equipment, only the limiter the manufacturer programmed, often at 250 km/h. It carries neither the same technical constraints nor the same legal framing, and it has its own article: Vmax Off — speed derestriction explained.

Legality and roadworthiness testing

In France, removing the DPF has been illegal on any vehicle used on public roads since the decree of 1 January 2021. The roadworthiness test now checks that the DPF is present, by visual inspection and by measuring particulate emissions.

EGR Off, by contrast, passes more easily, because the EGR is not checked directly — only CO and HC emissions are measured. A properly executed EGR Off generally stays within the emissions limits at test time.

In short

DPF Off and EGR Off are software deletes that solve real mechanical problems — a blocked filter, a sooted EGR, faults that keep coming back. On a road car in France, DPF Off has been illegal since 2021. EGR Off is treated more leniently, but still belongs to specific use cases.