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2004 BEW Limp Mode Boost Issue

26007 Views 12 Replies 6 Participants Last post by  Davidloc
Hi There,

I have a 2004 Jetta Wagon TDI with the BEW motor. The car has been going into limp mode nearly every day especially on very cold mornings while going up hill. I unfortunately I did not copy down the code that was thrown but it was related to an overboost condition.

***Start Edit
16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)
P0234 - 000 - -

I took car out for a test drive an was able to make it go into limp mode again and reproduce the fault code above. I also checked the MAF via VCDS and it seems to be fine as the actual tracks the requested up to ~800 or so and back again.

***End Edit.

Today I replaced all vacuum lines (one at a time), the N75 valve, and the check valve. By inspection the old check valve was broken (i.e. air flow in both directions = bad). I saw some minor wear on the vacuum lines but nothing special to note. I can freely move the actuator with my finger and have run the output test to verify that N75 is indeed moving the actuator under vacuum.

However, I am not convinced that the car is fixed. Please see that attached image of the VCDS scope screen. This plot is the result of revving the engine while in the driveway. The specified boost and the actual boost do not track as I think they should (per the 1000q faq). As you can see the actual is significantly higher than the requested.

Any ideas where to check next (MAP sensor maybe)? I would really appreciate any help that could be provided. I have searched the forums and faqs for weeks which led me to replace the vacumm system parts. Now it is time to ask for help directly.



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Replacement Actuator Installed in NJ


I read your post and instructions to change the BEW turbo actuator. You hit a home run! You are one crafty mechanic. I ordered the actuator from Idparts.com (1 X Smart Vane Actuator VNT-15/VNT-17) for 119.00 with free standard shipping. The part took 3 days to arrive. I only made a few minor deveations from your instructions. I did not remove the heat shield from the bracket. I just drilled out the rivets, drilled new holes for the replacement actuator and mounted it with new nuts. For the rod extension I could not locate a metric m6 threded rod coupling so I cut the adjusting nut out of the new actuator ball and socket mechanism for my coupling and cut the threaded part of the old actuator rod off, put that together and used that as my extension rod. I used 2 more new nuts to lock it in place and reinstalled the actuator to the turbo as per your instructions. All together my cost for parts was $ 125.00.
I too am dissapointed that VW won't sell a replacement actuator as a direct bolt on. That's just bad buisness. No one likes to be ripped off. A repair that is $ 2,000.00 when all you need is parts that cost $125.00 and maybe 2 hours in a shop for labor (total > $500.00) is wrong.
Anyway thanks a million! I am so glad I read your post.

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