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P0409, seized EGR valve – Fixed


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Subaru’s 2.0 diesel engine has a few faults, the one that seems to cause the most trouble is when the EGR valve fails. Not only does it hamper performance but it is also an MOT failure. Here’s how to fix it.

If you want to read the background then look at this thread.  I've been all over the web trying to sort this, chasing bad information.  The final pieces of the puzzle came to be by way of my friendly Subaru mechanic.


First thing first – what does it do?

When the engine is running, the valve allows some of the exhaust gasses to recirculate back into the engine. The purpose of this is to lower the Nitrous Oxide (Nox) emissions. It rotates through 70 degrees from fully closed and this is decided by the Engine Management Unit.

On full throttle, or when the engine is idling, the valve is closed. The valve opens in a very managed way depending on the speed of the car and the throttle position. All controlled by the EMU.


How does it fail?

Cheap fuel, short journeys. The carbon (soot) in the exhaust gasses accumulate in the valve and it eventually seizes. The motor in the EGR housing tries to move the valve but it doesn’t so the tiny little motor burns out and fails.  And this shows up as P0409. There is no optical sensor – it doesn’t exist. The only fix is to remove and replace the EGR valve.  Subaru part number 14710-AA740.

If you buy a second hand valve then chances are it’s knackered before you start. If the motor still works then remove the carbon deposits with carb cleaner so that the valve can move. They are filthy. You can buy a replacement from Subaru, or you can buy a pattern part. Subaru don’t make them, btw, just like they don’t make tyres.


How do you know that the EGR has failed?

Apart from Error Code P0409, you’ll see two warning lights – they’re on the bottom left of the dashboard display. What you’ll see is the traction control light and the engine management light. These come on together because of the knackered EGR valve.

In reality, traction control has now been disabled (MOT failure!), fuel economy is suffering and you won’t have the same acceleration as before. This particular loss is incremental and you won’t have noticed it. The Engine Management light is another MOT failure so you’ve really got to get this done.

I did this to my high mileage 2008 Outback. The pictures are of my car and I know it’s not a show piece so don’t start telling me! Why not print this out and have it with you as you do the work?


How to replace the EGR valve in 4 easy steps.

This isn’t difficult, maybe a little daunting but it’s easy to do. All instructions are with you standing at the front of the car, looking into the engine bay.

Here’s a list of what you’ll need:

  • New EGR valve

  • 2 x plastic bags

  • Socket set, short and long extensions

  • 12mm ring spanner

  • Copper-slip grease

  • Long nose pliers

  • Paper towel


Step 1 – Remove the Intercooler

  1. Take the black engine case off – it just pulls off.

  2. On the LHS, loosen 2x hose clamps on the intercooler inlet and remove the angled, black link pipe. Cover the remaining pipe with a plastic bag so nothing falls in. At the bottom of this pipe is the turbo.

  3. Loosen the hose clamp on the outlet (RHS) of the intercooler, leaving the pipe in place. This clamp is captive so just undo it.

  4. Undo 1x 12mm bolt on the back left of the intercooler, 1x on the back right and then the 2 x bolts on the support bracket. Remove the bracket. Whilst you’re doing this, move the pipe that is attached out of the way too – it just unclips.

  5. Be careful as intercoolers are delicate and expensive to replace!

  6. Standing on the RHS, remove the intercooler. The rotation releases the intercooler from the outlet pipe and remember to cover it with a plastic bag.


Step 2 – Remove the EGR valve

It is located at the top of the engine, on the LHS, behind the big cross piece.

Important for you to know that:

  • We are going to remove 2x studs from the exhaust side, and then 4x bolts which fix the EGR to the inlet manifold, and they must go back into the same place.

  • There are two gaskets and you don’t want to drop them.

  • There is a bolt which holds the coolant pipe to a frame and you don’t want to drop this either.

  • There are 2x rubber coolant pipes which attach to the EGR valve.

  • There is 1x electrical connector.


  1. The exhaust pipe that attaches to the back of the EGR valve, chrome coloured, is cooled. With a 12mm socket on a short extension, remove the bolt which secures the J pipe to the frame. It is located halfway down the square section on the wheel side. It screws in towards you. You find it on the LHS, just follow the pipe.

  2. At the end of this J shaped pipe, where it attaches to the valve, there are 2x 12mm nuts. You’ll need either a deep socket or a ring spanner. Loosen but do not remove.

  3. With a 6mm socket, remove the studs, bottom one first, catching the gasket. The gaskets are metal and could quite possibly be used again. This pipe is now loose.

  4. Using a 12mm socket and/or a ring spanner, remove the 4x bolts that hold the valve onto the inlet. At some point you will need to take the coolant pipes off too. Do not drop the gasket.

  5. Use the long nose pliers to remove the coolant pipe clamps, and pull the hoses off. You will lose a little coolant. If they’re stuck on (most probably!) use a right-angled pick or cotter pin puller to separate the hose from the metal pipe. Be very careful because if you damage these pipes…

  6. Unplug the electrics.

  7. Remove the valve by rotating it and up and out to the left. Remember how you do this because the new valve will go in the same way.


Well done, you’re half way there! Clean up – soot, threads and the merest of copper-slip, coolant, leaves etc.


Step 3 – Replace the EGR valve

Important to note:

  • Reversal of the remove, really. I had the slightest of copper-slip on all mating surfaces. What is needed will stay, what’s not will get burnt off.

  • Coolant only needs to be topped up if needed.

  • Careful with the electrics – they don’t like coolant.


  1. EGR valve in.

  2. Connect the electrics.

  3. Slide in the top two bolts and slide the gasket in so that it hangs off the threads of the bolts. Push the bolts through, into their holes and turn just enough so that the threads catch. Do the same with the bottom bolts. When they’re all ready, tighten them up.

  4. Coolant pipes on.

  5. Studs in. Top one first. Same trick with the gasket but feed the stud through, holding the gasket on the rhs. Hang the gasket off the top stud, feed in the bottom stud. Sorted.

  6. Tighten but not too much as you don’t want them to bottom out in the valve body whilst you’re still flexing your muscles. A snug fit. Tighten the nuts.

  7. Secure the pipe back to the frame with the remaining 12mm bolt.

  8. Intercooler back on.

  9. Engine case back on.

  10. Done.


Step 4 – Start the engine and remove the error codes

You’ll see the two error lights. They’re one the bottom left of the dashboard display. What you’ll see is the traction control light and the engine management light. If you plug your test kit in then the fault record still remains. You have to delete these records and then go for a drive to test it all out.

If you don’t have your own test kit, and your car failed it’s MOT then at the re-test, ask them to remove the codes.

You can buy test kit, and you can get an OBD2 plug and use an app on your phone!

And that’s it. I think you can give yourself a little pat on the back for a job well done. And you’ve saved yourself hundreds of pounds to boot!














EGR map.pdf

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  • 3 months later...

Hi, I've replaced my EGR valve on my 2008 legacy 2.0d (with a brand new one) and am still getting the p0409 code !!   

Has anybody got any ideas what I need to check next?

Thanks everyone.

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  • 1 month later...
  • 3 weeks later...
  • 6 months later...

Hi I have a 2010 Subaru outback 2.0 and I am also suffering from error P0409. I changed the egr for a compatible one, specifically for this one: https://www.ebay.es/itm/324030019509 After changing the error persists after the third boot. How did you solve it? Have you had to put the original Subaru egr? The problem is something else and I don't thank you very much.

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  • 1 month later...
On 7/9/2019 at 8:07 AM, diavlo1984 said:

Same, replaced, still get P0409 code and a hissing sound whilst driving.  Could the EGR cooler be leaking?

Hissing sound could indicate a split intercooler hose.

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  • 5 months later...

There is 1 step missing from the first post, which is, reset the learned value (voltage) for zero opening angle of the EGR valve. In the Subaru workshop manual it calls this the "Compulsory EGR learning" (ie adaption), however it can only be done with a Subaru Select Monitor which is $$.  If you are lucky and get a EGR valve that has exactly the same zero voltage, then it wont need to be relearned by the ECU.  

Denso (who made the original EGR) details the checks as: When the engine is stopped, the ECU tests then removes voltage from the DC motor inside the EGR and waits for it to settle on the springs. If the sensor voltage once it settles doesn't match the stored value then a counter is incremented. If that counter gets to 2, a P0409 is triggered. the MIL light is lit. If you clear the P0409 with a scantool or FreeSSM, then the counter goes back to zero and you get 2 more engine starts without the P0409. 

Replacement EGRs has a HAL3725 chip inside it https://www.micronas.tdk.com/en/system/files/downloads/files/HAL371x_HAL372x_HAL 373x_Programmable_2D_Position_Sensors_with_Arbitrary_Output_Function_1DSH_final.pdf which almost certainly has a different zero possition voltage to the original. The original is fully encased and mechanically different.

I wasn't able to find any scantool, FreeSSM, Romraider or low level SSM1/2/3 method of resetting the memory location storing the learning flags. Disconnecting the power for 30m and doing an idle speed reset that works on petrol cars does not appear to work on my ECU.

In the end I stripped the original ERG down, cleaned it with carb cleaner and discovered that the plastic intermediate gear had old grease and was slightly sticky. (my original code and the reason for replacing the EGR was a P0403 duty cycle code, ie sticking). After cleaning and greasing the valve always returns quickly to the same zero position with no sticking and has been restarted 5 or 6 times with no recurrence of P0409s.


It might still revert to a P0403 or P0409 after a long drive so please, if anyone knows how to trigger a Compulsory EGR learning process without a Select Subaru Monitor, please share. I dont really want to try and persuade a main dealer to reset it for me as I am sure they want to replace the EGR as well and they are 400 GBP new from an official source. (ie not the cheap eBay clones).


I have photos, of the insides of both EGRs, but can't seem to attach.



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Finally if you monitor the valve angle with FreeSSM you can see it follow the desired angle. When the ignition is turned off you can see it go through the cycle. It will go to a -ve angle, but should settle on 0. If you get measurements, then your wiring is almost certainly ok. While the P0409 is active, the ECU doesn't instruct the EGR to do anything, and so no readings. There is also a measurement in FreeSSM for the EGR learning status, which will always be completed, unless you have managed to reset it. FreeSSM is https://github.com/Comer352L/FreeSSM, Kits and leads available from eBay.

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  • 9 months later...

Hi David(from Hampshire),

Great post, thanks.

Having replaced my EGR with a new from eBay, cleared A0409 code from history/stored codes my Snap On Ethos scanner showed the target & actual valve openings were matching & 'learning completed' but after a decent run the lights/code returned.

Did yours remain off & still working ok or did you have to have it reset by Subaru please?

My local garage's scanner went deeper & tried to reset but although the lights/code are currently off my scanner shows the opening stuck on -5 with the target numbers changing as they should. My scanner now shows 'learning NOT completed'. Seems they've triggered the learning process but not completed it?

Vehicle is a 2009 Forester 2.0d 49,000 miles. I have cleaned & inspected it's original EGR so might refit it?

Any help would be appreciated.





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Hi Clive,

I finally fixed my EGR with the eBay replacement with metal gears, in the photo above followed by a visit to my local Subaru dealership who charged me for labour to put the car through the learning process ("Compulsory EGR learning") as documented in the Subaru workshop manual. I asked the technician was there any other way of getting the car to accept a replacement EGR ? He said, No. They all have slightly different output voltages, even the genuine Subaru parts, and the ECU needs to work out what the voltages are at set angles before it will accept them. I also asked if there was anyway of triggering the learning process with a non Subaru scanner or tool, or with some magic button presses. Again he said no, not they he knew.   He did say, if you are lucky you might get a part with close enough voltage output to match the one that failed. The output voltages on mine were about 0.1v different.

Since the Compulsory EGR learning was completed, I've not had any problems. no more codes. 
It took them 1h but 30m was waiting for the car to cool down enough to start the Compulsory EGR learning. Coolant needs to be < 60C or something like that.
Hope that helps.

If you find a way round going to the Subaru dealership, please share here.

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Hi Ian,


Thanks for quick reply.

Was your eBay replacement a new cheap one & Subaru were ok 'teaching' that one?

I'm hoping the local garage's diagnostic can finish the job, maybe with the help from the diag company's tech support, as it seems to have the correct page/software but we've prob not input the correct parameters or followed correct procedure......it too requested coolant to be below 60°C.....so looks promising?

I'll post make of diag if we're successful.



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Yes. Cheap eBay EGR, as shown in the photos I shared and the neither the dealership or the Subaru Select Monitor had any problems with it.

Once it is completed, the angle should read 0 degrees in the scanner with the engine off (ignition on) and the valve at rest position. 
The target angle and the actual angle only indicate that the DC motor inside the EGR can be driven by a PWM signal from the ECU to achieve the target angle, (which is good). Those 2 readings matching doesn't mean that the EGR valve is opening by the target angle, until the Compulsory EGR learning is completed, indicated by 0 degrees at rest. 

I am fairly certain that the Compulsory EGR learning measures the sensor voltage with the PWM signal at 0% then drives the PWM hard to 100% to get the valve fully open and measures sensor voltage. It might also repeat a few times and measure the sensor voltage at different PWM  % to check linearity. The sensor chip (a 
HAL3725) outputs 0 - 5V varying by angle.

My normal garage (not main dealer) said they didn't have the software to do it.  If your's can please ask them what diag software they are using.

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  • 2 weeks later...

Hi Ian,

Make of local garage's diagnostic is 'Red', no model number as it constantly updates + has tech advice.

It can set the EGR into learning mode, after which the car/ecu does all the rest after a 20 mile or so drive, now driven it over 50 miles. Dash lights are off.

Diag tech thinks it might be due to it being a non factory cheap replacement but aren't sure. They don't know of any way to make the learning complete after it's been started other than a 20 mile drive.

Have you had yours read on a diag since Subaru 'reset' it or have you not bothered as your dash lights have remained off.....as have mine?

Unfortunately when I read mine on my Snap On scanner the numbers are still not synced, actual opening constantly reads -5 but learning is reading not completed & I've

I'm thinking of unplugging mine to throw a code, hopefully it reads on my Snap On as a history code which after previously clearing history codes the numbers were synced but learning hadn't then been instigated......??







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Unfortunately when I read mine on my Snap On scanner the numbers are still not synced, actual opening constantly reads -5 but learning is reading not completed & I've now driven over 50 miles.

In my previous post the above paragraph somehow got put out of order so some might miss it thinking all has been cured, which it hasn't.

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When I checked mine after the Subaru garage put the car through learning, they were perfect, always returning to 0 when the engine was turned off. Not had any problems since. Compulsory learning didn't require the car to drive. They did it all in the workshop with the Subaru SSM connected.

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  • 5 months later...
my 2015 outback is throwing up a "P049B" code which is related to the egr, so i got the entire top end hot washed ($1300) and there error is still coming up.
The mechanic told me the EGR looked quite new too!
even had the mechanic drive with me today to see the code come up and the diag tool showed nothing wrong
has anyone experienced this and found a solution
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  • 3 months later...
On 8/24/2020 at 1:40 PM, ___ian___ said:

Finally if you monitor the valve angle with FreeSSM you can see it follow the desired angle. When the ignition is turned off you can see it go through the cycle. It will go to a -ve angle, but should settle on 0. If you get measurements, then your wiring is almost certainly ok. While the P0409 is active, the ECU doesn't instruct the EGR to do anything, and so no readings. There is also a measurement in FreeSSM for the EGR learning status, which will always be completed, unless you have managed to reset it. FreeSSM is https://github.com/Comer352L/FreeSSM, Kits and leads available from Ebay.

I'm mow starting to get "-20" as angle reading from EGR. During driving it can change to "-11" or even "0". Sometimes it works just fine after engine start i.e. "0" when ECU orders "0" and then follow ECU-ordered angles as it should.

I have noted that the axle on which the valve is mounted, and that is connected to the black sprocket, is worn and can be wiggeled back and forth. Can this wear make the sensor-readings go bananas?

If I apply 12V to the motor it moves the valve so it is not stuck.

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  • 2 years later...

Thank you so much. My wife's Subaru outback 2.0d started to light up as a x mast tree on the dash😅 engine light , parking brake cruise control and the stabilizer light. After much searching I found ot that's it the egr valve that was clogged up .

this post is just perfect for me so I can mend it👌🏻

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