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VW B5 Passat TDIs This is a general discussion about B5 Passat(>98 (2004-2005 in North America)). Non TDI related postings will be moved or removed.

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Old August 4th, 2016, 15:27   #1
DeliveryValve
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Default 16618 - Boost Pressure Regulation

Going up a mountain and floored the accelerator to try to pass a vehicle, the car went into limp mode. Coasted and pulled over, shut down the engine for a few secs, then started engine and went off my merry way without any other mishaps.

Plugged in the VCDS and it reported this...

Quote:
1 Fault Found:
16618 - Boost Pressure Regulation
P0234 - 000 - Limit Exceeded (Overboost Condition)
Freeze Frame:
RPM: 2142 /min
Torque: 336.0 Nm
Speed: 112.0 km/h
Load: 83.1 %
Voltage: 13.38 V
Bin. Bits: 00101000
Absolute Pres.: 2305.2 mbar
Absolute Pres.: 2590.8 mbar
So the list items to check. VNT actuator movement, N75 (have to read up on how to check it, any leads?) and vacuum lines.. Any other items I am missing?

One thing I am happy with... At least my engine is putting out the advertised 247 ft/lbs of torque with the stock ECM flash.



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Old August 5th, 2016, 14:01   #2
TheGrove
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My $.02 worth, if this is the only time it has done it chalk it up to a fluke and drive-more / worry-less. The 2004/2005 Passats have a habit of going into limp mode, I found mine used to do it most often when floored on a hill as well. I would say mine did it every 2-3 months out of the blue. I got pretty good about cycling the ignition while coasting down the highway instead of pulling over.
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Old August 5th, 2016, 18:14   #3
DeliveryValve
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Thanks for chiming in. Yes, this is the first time it has done this. I've been driving car around in flat land and it has been acting fine. I even had to floor it when I inadvertently turned in front of an on coming car. Luckily it didn't do it.

But interesting tidbit on your cycling of the ignition. You would shut down in neutral while the car was rolling and restart the car?


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Old August 6th, 2016, 04:10   #4
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Yes, pop into neutral turn the key back 1 click to off then start it back up.
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Old July 11th, 2019, 15:26   #5
DeliveryValve
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I had a revisit of this same issue a few days ago while driving up a long mountain grade causing a heavy load on the engine.

The last go around, I pretty much didn't do anything except an Italian Tuneup and the code never came back. Since then, I had a 16683 code 21,000 miles ago in Aug 2017 and replaced the N75 valve along with several of the cloth covered vacuum lines.

Upon researching again this issue, someone reported that the dealership replaced the MAF to fix this on their Passat. Can the MAF really cause 16618 or is the dealership blindly throwing parts at it and it was just a fluke as TheGrove previously mentioned?

However, I did find my snow screen clogged and yanked it out. All vacuum hoses and charged air hoses look good. Drove around doing the Italian Tuneup and acting like a mad man with several cycles of WOT's. No codes came up during that process.

I hope that does it. Because I don't really want to pull the turbo to clean VNT, plus I have to get back to the mountains this weekend. Passat Wagons are very useful with it's cargo space. If I didn't need it, I would be taking another vehicle for the trip.
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Old July 12th, 2019, 06:50   #6
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Are you certain you don’t have a boost leak somewhere? In my experience the system will tolerate small leaks for quite a while until something puts it over the limit.
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Old July 12th, 2019, 10:23   #7
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Thanks for the reply.

Visually the hoses look good and have a tight connection. I have a somewhat newer Factory turbo outlet hose and intake manifold elbow hose.

I really can't be sure if the connections are leaking just by revving the motor, it needs a load. I'll have to fabricate something where I can pressurize the system. Unless there is setup readily available or a process out there already that I don’t know of.

16618 is an overboost situation. Not sure if leaking hoses would cause that also. But leaking hoses can cause a 16683, P0299 - 000 - Control Range Not Reached which I had before on a blown hose.




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Old July 13th, 2019, 09:48   #8
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I put a cap on the turbo inlet and cut an ABS fitting to go on the outlet end of the hose going into the anti shudder valve. I had to use a continuous low pressure air flow to find a leaking O ring. Which looked fine btw.
Overboost doesn't seem consistent with a leak but I have seen limp mode with no codes multiple times.
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