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obd2 post Subaru Diesel DPF Light 1

Subaru Diesel DPF Light Outback Forester

Checking your Subaru Diesel DPF

subaru dpf
subaru dpf

Subaru has a few models that have issues with the Diesel DPF and the fact that most people do short drives does not help the fact and you will get DPF issues with the light flashing or higher fluid usage.  

What we will discuss here is how you can use the OBD-AUS BTV4 Bluetooth scan tool* to watch this data on your phone which will allow you to monitor what is happening and have more of an idea about what is going on with your Subaru Diesel DPF and engine.

What we discuss below are the settings (PIDS) used for getting the extra DPF information. We will also recommend one of our scan tools that will allow you to do a manual DPF Regeneration. This is for the EE20 engine.

What will you need to perform the scan?

Phone or Tablet: Apple or Android does not matter
App: We suggest Car Scanner ELM OBD (apple) or Torque (Android) you will need full version of these apps so that is $6 to $9.
OBD-AUS Scan Tool*:

obd aus bluetooth scan tool obd2 scan tool a
obd aus bluetooth scan tool obd2 scan tool a

Steps to follow

1. Download app
2. Plug in OBD-AUS and connect to it.
3. Open app and make sure it is reading data.
4. Go into the app settings and custom PIDS or sensor button.
5. Enter the PIDs in below to view data from these extra sensors.

Actual PIDS for Subaru Diesel DPF

EGT at catalyst inlet
– PID 22003c, unit °C, Max 800, Min 0, equation ((A*256)+B)/10-40
– ?This is the one I look at for avoiding engine damage. 200-400 is normal. 600 is normal in the first minute or so of a regen cycle. 800 is definitely bad and you should park for a bit.

EGT at DPF inlet
– PID 22003c, unit °C, Max 800, Min 0, equation ((A*256)+B)/10-40
– ?Not really that useful, I think the ECU uses this to estimate DPF temperature? No idea. But after your first regen for an engine cycle this will go high and stay high. I’m not sure if this is actually at the inlet or the outlet.

DPF Regen cycle on
– PID 22125b
– ?If you set this up as an on/off it tell you when the DPF is regenerating. Important to know because at the start of the regen cycle the EGT @ the cat will go high and you shouldn’t be concerned if this light is also on.

DPF temperature (estimated)
– PID 22114c, unit °C, Max 800, Min 0, equation A*5-40
– ?Not that useful but fun to know!

Soot accumulation ratio
– PID 22114d, unit %, Max 100, Min 0, equation A
– ?How much soot is currently in the DPF awaiting regen, seems to trigger ~ 65%

Cumulative ash ratio
– PID 221149, unit %, Max 100, Min 0, equation A
– ?I think this is calculated from the exhaust pressure before and after DPF, you can think of this like the lifespan of your DPF unit. Mine is worked hard and is at 72% at 165k KMs. The more ash, the less available soot capacity, the more frequent the regens, the worse the economy and power.

Distance since last regen
– PID 221156, unit km, equation A*256+B
– ?Mine seems to be every 25-30km, yours will depend on your cumulative ash ratio, the climate you live in, and the engine oil you use.

Distance to oil change
– PID 221155, unit km, Max 2000, Min 0, equation A*100
– ?This is calculated from oil dilution which itself is estimated. I use this to remind me to do the park light/defogger dance (see your manual) when I change the oil.

DPF Regen Count
– PID 221157, equation A*256+B
– ?How many times your DPF has done a full regen

DPF Regen Attempt Count
– PID 2211a1, equation A*256+B
– ?How many times your DPF has done at least 50% of a regen (including full regens)

Thanks for OzFozDave and the Subaru Diesel Team for the above PIDS.

Our Final Word

Now that is basically it, and you can keep an eye on what is going on with the Subaru DPF on your car. All these will be shown live on your phone*, and you can design your dashboard, so it is how you would like it.  


The steps above may or may not work on some Subaru vehicles. This post only serves as a guide on how to monitor DPF details on some Subaru vehicles, and as such OBD2 Australia does not fully guarantee compatibility, and will not be held liable for any damage caused by your vehicle by performing steps above.

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