T2 V6 TDI Overboost Sporadic

MrCypherr

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Got a T2 v6 TDI that maybe one or twice a month comes with a overboost fault. When it comes on, sometimes its just a cruising and not under load. Checked all the hoses/lines, nothing seems damaged or leaking. Checked the MAP sensor and the pressure sensor, No concerns there. Visually seems okay. I performed a output test on the control module of the turbo and it seems to be moving properly. Doesnt seem jammed. Now this is very sporadic cause I've driven the car very hard and it never happens. Its very random when it happens cause it could be a cruising speed or maybe some hard pedaling. Heres screenshots of the fault and the open/close of the output test.

Car is tuned with Malone with a delete. Im suspecting maybe a sticking actuator when it comes on. Maybe just every so often. Not 100% sure though. Hoping someone has some idea.

Thanks!




 

TurboABA

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Since it's tuned, I'd log the actual vs requested to see what's happening.
Check all your charge tract, especially the plastic IC tanks which could fail at that age with the added pressure increase, etc.
You may have a small crack\leak that only "opens up" at higher boost pressures. I'd do a pressure test on the charge system if you've already ruled out the N75 (edit: maybe I should pay attention because we're not talking about the 2L so no such sensor here.... but you said the J724 appears to be good) G31... maybe ever replace the MAP sensor as they are cheap enough.
 
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TurboABA

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Check and maybe replace the O rings at the SMICs as a leak there wouldn't be easily detected while simply crawling around under the hood visually, etc.
 

TurboABA

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Look at the FF data...
There's no labels on that, but based on the values, I will jump to the conclusion that the order is, Actual, Requested & Ambient.
There's a major difference between Actual & Requested..... ~ 13.7psi
 

MrCypherr

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Gonna pressure the charge system since I didnt have a tester at the time. Gonna see if I can snag a good MAP sensor. Problem is that this happens so sporadically that its gonna be hard to diag lol. Also is it just vagcom or can I get the proper FF labels on that? Gonna get a proper road test log in and see whats actually happening.
 

TurboABA

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The OEM MAP is inexpensive..... but I think you have a leak as per my latest remark.
It should happen ALL THE TIME when you're asking for full boost... if you're granny driving, it may not be significant enough to throw a CEL.

I'm not sure that there's something you can do for the FF labels.
Just go into MBVs and log the respective pressures. There's a search box under the advanced MVBs which makes it easy to locate whatever you're after.
 

MrCypherr

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Thats what I was wondering as well. Considering that the car has be driven hard and soft, and not triggered the overboost fault but the odd random time it triggers it, is making me think that it isnt a huge leak and maybe a faulty reading sensor. Id assume a leak would trigger it all the time when WOT. Gonna give the charge air tester a try and log it properly on a road hoping i can trigger it.
 

TurboABA

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Well, you can see in the FF data that it happened 8 times.... so it might just be the ECU logic that waits for the condition to repeat X amount of times before it triggers the code. It's clearly not a one or two time occurrence like you're suggesting.
 

MrCypherr

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Its usually once or twice the fault triggers and car goes into limp mode. I should have specified. I guess its seeing it more often and not exactly triggering it.
 

TurboABA

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I only have your posted FF data to use when formulating a theory.... I have no idea when you cleared the codes last, how much you drove since, etc.
Blow all the codes out and do your normal drive\commute. Scan again at the end of the day and determine if that drive is enough to repeat the fault 1 time or 10 times....etc. Based on that info, change your time between clear & rescan accordingly in order to determine how much driving it typically takes to get to limp mode, etc.
 

TurboABA

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Is there any chance that the previous owner swapped\replaced your J724? Because these needs a special tool to be calibrated if ever replaced.
You might also have yours original and on it's way out. You could run the output test on it over and over a bunch of times to see if it hangs up after 5 or 8 back to back tests..... maybe it's possible that it only fails\sticks after it heats up during a longer drive or extended "actuation".
 

MrCypherr

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Ill get my vagcom and check it to see if the screen is like that one you posted. Buddy had the car for 3 years now and it only started acting up recently but very sporadic. Atleast throwing the code. Running the output test and couple times and honestly didnt see anything that could show fault/wear but then again, who knows whats actually happening. May look okay but be on its way out the odd times it throws it.Gonna clear the codes and monitor it every day to see when and how many times it happens that day. Right now if Im throwing parts at it, its gonna be the actuator but going to check a few more things like you mentioned before i start replacing.
 

TurboABA

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Depending on what turbo is on there, I believe some actuators can be replaced.... but you need a specialty VAS tool to set the limits properly.
 

MrCypherr

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Since its just you in here TurboABA, 😆 Figured out it was a faulty MAP sensor sporadically reading incorrect at times. Swapped in a new one and things are reading more within spec now.
 

MrCypherr

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Yep! Had a good known one laying around and swapped it in back then when you mentioned it. Still did other checks but yeah, good call!.
 
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