David in Hampshire

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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Top quality post mate I'll pin it when i get to a PC 😊

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