Let’s face it, the Diesel Particulate Filter (DPF) is a double-edged sword. It keeps our beloved Subaru Foresters clean but can be a real pain (and a drain on the wallet) when it comes to forced regenerations. We’ve all been there: the dreaded DPF light comes on, and a trip to the mechanic for a reset or forced regen leaves us $150 lighter. There has to be a better way, right?

The $10 Solution: Taking Back Control

Fear not, fellow Forester Diesel owners! There’s a simple and surprisingly affordable solution: a trusty OBD plugin and a compatible mobile app - ODB scanner (available for iOS and Android). Here’s the beauty of it all: for around $10, you can get an OBD scanner that plugs directly into your Forester’s diagnostic port. With the right app, this little device unlocks a treasure trove of information, including all the vital DPF sensor readings.

Unlocking the Secrets of Your DPF

The key metric we’re after is the Soot Accumulation Ratio. This tells you exactly how full your DPF is. In most Subaru Foresters, the DPF regeneration cycle kicks in automatically when this ratio reaches around 60%. The good news? The regeneration process itself is fairly straightforward. All you need is a sustained drive (10 - 15 minutes) at a moderate speed to allow the exhaust gas temperature to rise and burn off the accumulated soot.

See pictures for the proof - I completed this DPF Regen in 9 minutes

DPF in progress

  • Time started 15:58
  • DPF Active Regeneration Switch is 255
  • Soot Accumulation is >60%
  • DPF temperature goes up to 550 / 600C


  • Time end 16:06 (8 minutes!)
  • DPF Active Regeneration Switch is 0
  • Soot Accumulation has dropped
  • DPF temperature starts to drop back to 250C
  • Distance since last regeneration is reset

Empowering Yourself with Knowledge

With your handy OBD scanner and app, you can now become the master of your DPF destiny. Here’s the winning strategy:

  1. Monitor your Soot Accumulation Ratio: Regularly check the app to see how full your DPF is getting.
  2. Plan Your Regeneration Drives: When the ratio approaches 60%, schedule a highway drive of at least 15 minutes. This allows the natural regeneration process to take place, potentially saving you a trip to the mechanic.
  3. Stay Informed: The app can provide additional DPF-related data, allowing you to stay on top of your vehicle’s health.

The Takeaway

By taking control with a simple OBD scanner and app, you can transform your relationship with your Subaru Forester Diesel’s DPF. Empower yourself with knowledge, save some cash, and keep your trusty Forester running clean and happy for miles to come.

Important bit of a Disclaimer:

While this method can be effective for some drivers, it’s crucial to remember that it’s not a magic bullet. Ignoring a failing DPF system or neglecting proper maintenance can lead to serious engine problems. If you suspect a more significant DPF issue, consulting a qualified mechanic is always recommended.

Tags: Subaru Forester, DPF, DIY Maintenance

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Damien Saunders
An experienced management consultant and business leader interested in digital transformation, product centred design and scaled agile. If I'm not writing about living with UCTD (an autoimmune disease), I'm probably listening to music, reading a book or learning more about wine.
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