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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.

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.

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.

After replacing an EGR with a new EGR you must perform a EGR angle learning, so the ECU can learn the voltages from the position sensor that represents 0 degrees. If the ECU doesnt relearn the new position sensor, when the engine is turned off it will detect a fault (you can hear the ECU testing the EGR when you turn the engine off). If it detects a mismatch 2x in a row it will throw a P0409. Clearing the P0409 code gives you 2 more goes but it will always come back without EGR angle learning. 3 options to fix (assuming no other codes and no wiring faults) 1. Clean the original EGR, open it up fix anything that stuck, stiff or broken, but keep the sensor the same. 2. Take the top of the original EGR and put it on the new EGR, hoping that the magnets indicating angle are in exactly the same position. (cheap(er) ebay replacements use different sensors and internal design even though the part numbers match) 3. Get someone (main dealer) with a Subaru Select Monitor to perform the EGR compulsory learning operation. (search follow the installation on EGR here http://jdmfsm.info/Auto/Japan/Subaru/Legacy_Outback/2008/Legacy 2008/index.html) There are 2 other options for the really persistent DIYer. Keep replacing the EGR till you strike it lucky and get one that matches perfectly. Really take the EGR apart and get the 0 degree voltage to match by moving the magnets on the valve shaft. If anyone knows of a scantool operation that will do the reset please say. Disconnecting negative for 30min doesn't do an EGR angle learning reset. I expect my EGR will break again and would love to know the dark magic to do it.

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.

BTW, thanks for the tip about 2 gaskets. Found it resting below the EGR after 160 miles of driving. Here are the photos.

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.