OPF/GPF Off — disabling the petrol particulate filter

OPF/GPF Off disables all of the petrol particulate filter logic in the ECU software: soot load calculation, differential pressure sensor monitoring, regeneration and the limits the ECU imposes when the filter is blocked or faulty. For tuners: send us the original file and get a ready-to-flash file with corrected checksums, on average in 30–60 minutes.

Why petrol engines got a particulate filter

Euro 6 sets a particle number limit for direct-injection petrol engines: 6×10¹¹ particles per kilometre. For the first three years manufacturers were allowed ten times that, so the limit took full effect in September 2017 for newly approved models and in September 2018 for all new cars. In real-world driving many direct-injection engines could not meet it, and the filter became standard equipment.

The first production petrol filter appeared on the Mercedes-Benz S 500 in 2014. Volkswagen started fitting it in June 2017 to the 1.4 TSI in the new Tiguan and the 2.0 TFSI in the Audi A5, then rolled it out step by step to all of its direct-injection TSI and TFSI engines. The names vary, GPF (gasoline), OPF (Otto) or PPF (petrol), but it is the same part.

How the filter works and cleans itself

Inside is a ceramic honeycomb with alternate channels plugged: one channel is open at the inlet, its neighbour at the outlet. The gas has no way out except through the porous wall, and the soot settles on it. The filter sits behind the main catalyst or carries a catalytic coating of its own, in which case it replaces part of the catalyst. It can be mounted close to the engine or under the floor.

What sets it apart from a diesel DPF is the exhaust chemistry. A petrol engine produces far less soot and runs a hotter exhaust, so the filter mostly cleans itself as you drive. The catch is oxygen: at λ = 1 there is almost none in the exhaust. According to AECC, under those conditions soot ignites at about 650 °C, while with excess oxygen it starts burning at around 500 °C. Oxygen arrives when the driver lifts off and the ECU cuts fuel: the cylinders pump clean air into the exhaust, and the soot on a hot filter burns off.

A car used for short trips, in traffic or with a cold engine never gets the filter hot enough, so soot builds up. The ECU then steps in and raises exhaust temperature through ignition timing and mixture. Once the filter is heavily loaded, the ECU starts protecting it from overrun fuel cut instead: a sudden rush of oxygen into a hot, loaded filter can make the soot burn too fiercely and overheat the ceramic.

What the ECU does as the filter loads up

The ECU tracks soot in two ways: with a model (how much soot the engine has produced under the conditions driven) and with a differential pressure sensor, usually piped to points before and after the filter. More soot means a bigger pressure drop. The same reading is used to estimate ash, the residue of burnt oil, which regeneration cannot remove. Porsche, for example, recalculates ash every 1000 km and stores a fault at 100%. As the load rises, the ECU applies restrictions in stages. Here is how it works on the Porsche 911 (992):

Load levels 0–6 from Porsche Technical Information 52/25 for the 911 (992) from model year 2024. Other makes use their own thresholds, messages and limits.

Why GPFs clog and which fault codes you will see

• Short trips and a cold engine. Mazda's owner's manual specifically mentions repeated trips of 5 minutes or less.
• Oil consumption. Ash builds up faster and cannot be burned out. After an oil consumption repair, Porsche specifies new filters and an oil change.
• Ignition and injection faults. Porsche has them fixed before any work on the filter, and if the measured soot load is higher than the calculated one, the fuel system is checked.
• The differential pressure sensor and its lines. A cracked, kinked or detached line gives a false reading, and the ECU logs a fault on a perfectly good filter.

These are generic SAE J2012 codes shared by diesel and petrol filters. Many code lists call them "Diesel Particulate Filter…", even though on a petrol car they refer to the GPF. BMW (the F40 1 Series with the B38 engine, for example) also uses its own codes for the same faults.

What OPF/GPF Off changes in the software

Clearing the codes with a scan tool is not enough: the ECU keeps counting and turns the light back on. So the logic in the file itself is changed, and the ECU stops managing the filter.

The catalyst, lambda sensors and the rest of the calibration stay as they were. If the catalyst comes off together with the filter (on some cars they share one housing), add CAT/LAMBDA OFF to the order. Stage 1 or Stage 2 can go into the same file and the same order.

Disabling the logic adds no power by itself: the engine runs on the same calibration. In AECC testing a healthy filter raised neither fuel consumption nor CO₂, and tuners mostly talk about sound, since the filter noticeably quietens the exhaust. So OPF/GPF Off is mostly needed in two cases: the filter is blocked or damaged, or it comes off with a new downpipe for Stage 2.

What to check before flashing

• Before ordering, read the fault codes and check the pressure drop and soot load in live data. That tells you whether the filter, the sensor or the lines are at fault.
• If the filter is removed, blank off the sensor line ports. Whether the Δp sensor should stay connected depends on the ECU: mention it in the order and we will advise.

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 OPF/GPF OFF. If the catalyst is coming off too, tick CAT/LAMBDA OFF, and add a Stage if you want one.
3. Get the finished file with recalculated checksums, on average within 30–60 minutes.
4. Flash the file, clear faults in all modules and check after a drive with a fully warm engine that the filter messages have not come back.

The option is available mainly for Bosch MG1, Continental Simos and SDI ECUs, and the full list by make is below. If your ECU is not there, send the file with a request: we will check the software and tell you whether there is a solution.

Disabling the particulate filter increases particle emissions and changes the vehicle's emissions class. 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. 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.