BRM Turbo actuator troubleshooting

Hey all, got a question for you all about the turbo acuator that I have been having problems with. Symptoms while driving are surging while at cruising speed, and on takeoff (if I push it) the car will throw a cloud of smoke and stumble over itself.

The relevant codes are p2654 (turbocharger boost control position sensor circuit: signal too low) and p0234 (boost pressure regulation, overboost condition). I'm assuming that code 2 is caused by the first code. When looking at MVB 43.2 KOEO, I see 100%, rather than what I believe it should be (0%). If I jump pins 2 and 3, MVB 43.2 goes to 0%. If I understand the system correctly, that percentage should change as I move the actuator in and out (by hand, I have the actuator removed), but my actuator does not report any changes in the MVB. When I hook up the actuator for an ohm test, I have an open circuit between pins 1-2 and 2-3, and 112 (at the 200k setting)between 1-3 (and I believe that isnt what im looking for). There are also no changes to that reading when the actuator is moved. That indicates a trash G500 right? If someone could test theirs and post back or confirm that I have readings that are out of whack, I would appreciate it.

Is it common for the electronics in the sensor itself to go bad? From most of my reading, it seems as though the problem is usually related to leaking rubber seals, or for the body to be rusted through.

One other thing, I have double checked wiring (visually and resistance tested), as well as voltage (5V between pin 1&3), and all hoses (everything holds pressure for 4-5 minutes). The internal vanes move just fine.

How many miles are on the car?

Just under 200k

Is it tuned? If so I believe your tuner could probably remove the smart feedback if it is truly the electronics causing the issue.



With that many miles if it is the original turbo it is probably the VNT vanes getting caught though.



If you end up replacing the turbo get a turbo without the smart actuator and your tuner can remove the smart feedback from the tune.

No tuner. Car is bone stock. It seems to me like the vanes move how they should, with the actuator removed, the vanes move easily, and when I put pressure through the hoses, it moved at 3" and topped out at 17. I could be missing something there.

Usually they move freely through most of the range but the get hung up at the beginning. Usually this makes the car sluggish and smokey when first starting to accelerate and then as the car applies more vacuum it eventually breaks free and then you get a big surge of power.



Past that I am not sure how to try to further diag it. The BRM is very fun with a tune, when I was in your similar situation I got an upgraded turbo without the smart actuator and had Malone tune all the smart actuator stuff out of the tune and that was that. You could try a new smart actuator but I hear they are tricky to get dialed in and they are expensive, ~$370.



If you get a a new OE turbo you run the risk that the problem is with wiring or something else other than the actuator.

That's a good point. I did test the actuator, and it responded as it should under pressure applied by the mityvac. If it was carbon build up, it shouldn't throw the 'circuit low' code tho right? I would assume it would just throw and over/under boost code?

It might be worth getting a tune for it. Ive got to make sure I get everything straightened out prior to tuning though. If I can't get it to run right, its probably time to pull the turbo and clean it. If that doesn't get it, I'll start looking into upgrading turbos.

Yeah, you should be able to tell with the mity vac if it is getting stuck I would think. It should move very smoothly throughout the whole range. If it is then it really could be a smart actuator electrical failure or other electrical problem. If that is the case the a tune could be your fix. I would see if Malone is able to just tune that smart actuator out then you might be good to go. If it doesn’t fix it and it ends up being the turbo you aren’t really out anything because then you can just buy an upgraded turbo and you would need a tune for that anyways. I would run all of this by Malone tuning before you go down this road but they are usually pretty good to work with. They tuned a bunch of stuff out of my BRM, including the smart actuator, ASV, EGR, etc.

Might be worth doing the zip-tie mod just for good measure. It won't hurt anything even if the end point is correct.

Good point, when I did the zip tie mod my zip ties kept melting so I ended up using wire. OP, if you do this I recommend wire because you can pre shape it into a loop to more easily catch the end of the actuator rod around the bolt.

In my opinion you should only do this if you have VCDS, it is easy to overdue it.

There exists such a thing a stainless steel zip ties. I bought some on eBay in order to do the zip tie mod, but then concluded that I did not need the mod after all.

I tried metal zip ties but they are super hard to maneuver into the space in my experience. Wire can keep an oblong shape and the you just twist it a little to tighten it more for adjustment.


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I did plastic ties, foil-wrapped plastic ties, solid metal ties, ratcheting metal ties...they all break sooner or later.


I just changed to a braided cable and ferrule (Ace Hardware) which has been in place for about a couple of months, time will tell. All you really need is 12in worth of cable, mitivac, and lots of patience.

Quick update, I pulled the actuator off, and confirmed that the diaphragm is fine. I am awaiting a used actuator.
Now i am wondering about something else: seems like the vane actuator lever on the turbo (with the actuator removed) is a bit sloppy. As in it moves without much resistance. I'm wondering if that means that the actuator ring is shot? It's tough to gauge normalcy, since I haven't played with one of those before. Current plan is to remove turbo and take it to a shop to see what they can do for me on a rebuild, or at least they can tell me what to think about it.
I have watched a few youtube clips where people are moving the actuator lever, but its a bit difficult to be certain how hard they are pushing on it to get it to move, plus most of them are coked up, which is why they are playing with it in the first place. Any thoughts?

Well I'm about frustrated with this project. I replaced the actuator and as predicted, it took care of the 'circuit low' code, but not the overboost issue.

N75 valve seems fine,and, as many other people have stated, it rarely fails. I applied voltage and vacuum to it with the mityvac, and it operated the actuator rod as expected (starts moving at 6”, full travel at 17”).

In the charge pressure control test, the boost moved from 867 mbar at idle, and 805 (9.9% duty cycle) to 958 (90%) (I'm at ~5000 elev.), which indicates to me that the actuator rod is adjusted correctly (as per the VCDS procedure described in the turbo stop screw adjustment wiki).

During real driving condition, it is still overboosting significantly. The comps of requested boost and actual boost aren’t even close (up to about 1683 and 2570, nearly 900mbar over requested), and I am getting what I can only describe as turbo bark (similar to my 6.0 powerstroke when it had an intake restriction, which caused it to build too much vacuum, and make a ‘chuff chuff chuff’ sound after easing up on the throttle after boost). The car also feels like it gets stuck at high revs, although not nearly as bad as it was. I can post graphs if that helps.

I get an itchy feeling that I am looking at a worn control ring, but to confirm that I will have to remove the turbo.
** Update: Turbo off, has some shaft play on the exhaust side, although not enough to hit the housing, and a worn control ring.

When my actuator failed I drilled a 1/4” hole in the top and a 1/2” hole in the side. I put a wing nut through the side and a 2” full threaded bolt in the top. Simply adjust the bolt until the optimal position is found. I locked mine three years ago and it works great. I get about 45.6 mpg this time of year and about 50 mpg during summer.


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I had an issue with the n75 a few years ago.... turned out it had partly failed... if you have a vcds, there is an output test for it.... My numbers were a little off.... I did not know what the correct numbers should be, but my mechanic replaced the n75 and it was fixed....

http://forums.tdiclub.com/showpost.php?p=5200093&postcount=17

sooperdooper said:

Well I'm about frustrated with this project. I replaced the actuator and as predicted, it took care of the 'circuit low' code, but not the overboost issue.

N75 valve seems fine,and, as many other people have stated, it rarely fails. I applied voltage and vacuum to it with the mityvac, and it operated the actuator rod as expected (starts moving at 6”, full travel at 17”).

In the charge pressure control test, the boost moved from 867 mbar at idle, and 805 (9.9% duty cycle) to 958 (90%) (I'm at ~5000 elev.), which indicates to me that the actuator rod is adjusted correctly (as per the VCDS procedure described in the turbo stop screw adjustment wiki).

During real driving condition, it is still overboosting significantly. The comps of requested boost and actual boost aren’t even close (up to about 1683 and 2570, nearly 900mbar over requested), and I am getting what I can only describe as turbo bark (similar to my 6.0 powerstroke when it had an intake restriction, which caused it to build too much vacuum, and make a ‘chuff chuff chuff’ sound after easing up on the throttle after boost). The car also feels like it gets stuck at high revs, although not nearly as bad as it was. I can post graphs if that helps.

I get an itchy feeling that I am looking at a worn control ring, but to confirm that I will have to remove the turbo.
** Update: Turbo off, has some shaft play on the exhaust side, although not enough to hit the housing, and a worn control ring.

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Thinking about this, it seems to me that if the turbo actuator position seems to be correct according to the Mightyvac vacuum measurements, then whatever is controlling the vacuum to the actuator must be faulty. Both the ECU and the N75 come to mind, but perhaps there are other things that could account for flawed vacuum control to the actuator.

Agtech4020 said:

When my actuator failed I drilled a 1/4” hole in the top and a 1/2” hole in the side. I put a wing nut through the side and a 2” full threaded bolt in the top. Simply adjust the bolt until the optimal position is found. I locked mine three years ago and it works great. I get about 45.6 mpg this time of year and about 50 mpg during summer.


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Click to expand...

So your turbo is no longer variable just maximum boost all the time?


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diesen said:

So your turbo is no longer variable just maximum boost all the time?


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Click to expand...

Correct it is no longer variable but it’s not set on max boost. When the actuator fails the turbo is stuck at minimum boost. If you tie it at max boost the car goes to limp mode once it senses a over boost condition. I basically use the jack screw and turned it in trip by trip until I found the spot that gave the most boost without setting the over boost code.

When I initially did the mod I intended it as a temporary fix. After a few weeks I found my mileage didn’t change and the overall performance was about the same. The only time it gives me trouble is if I get into steep hills on the expressway. Oddly enough my engine lamp even want off after a while.


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