Forester e-Boxer GPF issues

I did expect that GPF warning light would lit on some day but already at 2300 km! It was normal Tuesday morning when I started engine, I was heading to work. Immediately after self check car lit the orange symbol among with alarm beep, advising me to consult with the user manual. I did not care to drive regen cycle during morning rush hour. So I decided to go work normally and then later to drive the needed cycle.

What is Gasoline Particulate Filter (GPF)

I bet it is evil invention of the European Union that car makers are forced to implement. Alike diesel cars have Diesel Particle Filters (DPF), now gasoline cars (specially direct injection) have similar variant of that filter. Purpose is exactly same, to catch emissions that are harmful to the nature and people. Instead of polluting those particles to air, there is a separate “trap” (filter) where these pollutions are stored. Car should automatically burn these particles during the regeneration process. To get even started, engine needs to be fully warm. This can be problematic in certain situations. E.g. If you constantly drive short distances. Short distance can be defined so that, if engine does not reach normal operating temperature, then it is too short distance. So you need to take into account outside temperature too. I.e. obviously engine takes more time to warm up fully in -20C than in +20C

When the GPF light is lit..

User manual speaks WHEN the light is lit, not IF the light is lit. Sounds that Subaru is even assuming that light will be lit at some point.

So when that happens, it is quite easy job to start regen process. You need to drive:

1) Drive over 60 km/h
2) Keep rpm between 2000 – 2500 (transmission in manual mode helps)
3) Coast every now and then 3 to 10 seconds
4) Keep driving about 30 minutes

If the light starts to flash, then you need take the car quickly to the maintenence. They are able to do “forced regen”. So the whole story seems to be pretty much same as with the DPF filters.

Regen procedure

I had a chance to leave work early today. So I wanted to deal GPF issue right away. Quick review to the user manual before driving. I tried my best to do exactly as instructed. I headed to highway as there I can drive fast enough, keep high enough rpm (but not too high) and drive long enough. Nearly twenty minutes passed and light was still there. But then suddenly it went away. Problem solved for now.

With this experience I did not notice any difference how the car behaved or sounded. Probably I will notice difference later on, once I gain more experience and I am able to tell difference when the burning process is ongoing. According to the user manual there might be difference, e.g. how engine sounds. Could be bit louder during the process.


March 14th, luckily no issues since the February 18th. I did change bit my morning routines on way to the office. To avoid few traffic lights. Then on last week or two there has been longer distance driving. So probably that helps too.

April 30th, no issues so far. Distance traveled now over 5000 kilometres. Due to COVID-19 my short distance driving has dropped significantly and also days are getting warmer all the time as we are heading towards summer.

I expect that the summer time goes without any issues. If issues reoccur, those will be next time during the winter time.

May 8th, I though that I would not face GPF issues during spring / summer time. I was wrong. It has been fairly warm recently I have been driving more longer distances than short ones. So it was a complete surprise that car advised me to drive the regen procedure.

I had some business to Helsinki, where I would need to drive through the city. But before arriving there I had roughly 15 minutes of driving in highway. This was not enough to the regen procedure and light did not go off. I drove same way back and engine was already much warmer as the stop in the city was fairly short.

This time regen was successfully and light went off roughly after 15 minutes highway driving.

November 2nd, no issues since may

November 9th, I kind of knew it. Just few days after I mentioned that I have been without this GPF issue, light lit on again. I learned recently that according to Subaru, warning is actually informative type of message. Similarly as cold weather warning is informative. The difference is here that user is required to take action, in order to get rid of the “informative” message. So I disagree with Subaru regarding this. In my opinion it is advisable to take care of GPF warning soonest. At this point it is unclear for me that how long you can drive before doing manual regeneration procedure. I also added new column to the table. Outside temperature should be interesting information to check later on if it has any impact, how often warning comes.

November 23rd, two weeks and roughly 300 km and light was lit again! This worried me first and I almost decided to download RAV4 plug-in hybrid pricelist to my computer but then calmed down. My driving profile needs a change. I need to drive highway on weekly basis and see if that helps. I also decided to write a fresh blog post regarding GPF issues, since this light seems to lit on quite frequently.

December 15th, I though that driving highways at least weekly would solve this GPF issue topic for good. But seems that I am still getting these warnings way too frequently. 15k km / yearly service reserved and they will apply also an software update regarding how GPF works. Really looking forward that to solve issue.

5th, Jan 2021, Car had the first scheduled maintenance and also GPF related software update was installed. Update improves soot accumulation estimation and therefor it should reduce GPF warning illumination. Looking forward it helps!


Below is the table where I gather all GPF related issues. Really hope to keep this table as short as possible.

DateOdo meter (km)Regen durationOutside temp.
10.11.20201132015+1 C.
23.11.20201164225+6 C.
15.12.20201252440+3 C.
5.1.202113221GPF update in the serviceN/A


  1. Happened to a friend’s car at about 3700km, especially in the latest months with quarantine, thus driving seldom and always on short distances (typically <5km, rarely between 5 and 10km).

    As soon as the GPF popped up, I drove on an extraurban road (about 1km over 60km/h in manual gear keeping RPM above 2000) and then on a motorway (about 3km).
    On that motorway, I was driving at about 100 km/h maintaining the RPM between 2000 and 2600 (5th gear in manual if I remember well). Once at 2600 RPM, I released the gas pedal for about 6 or 7s till the rpm went back to 2000. I did this for like 3 times and the GPF light turned off.

    The whole procedure I think took me like 10m and few kms. Maybe just lucky because I did it the day after the GPF signal was on.


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