VW TDI forum, Audi, Porsche, and Chevy Cruze Diesel forum banner

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.



See less See more
1 - 4 of 13 Posts
You're on the right track. Boost is way off. Some possibilities : bad wiring on VNT actuator can, bad wiring to MAP, MAP sensor. When you say that you can freely move the actuator with your finger, there should be spring resistance in 1 direction and it should spring up by itself while returning to rest. If the actuator is disconnected you should be able to move the lever on the turbo w/o resistance.
The failure in the VNT actuator wiring is normally right at the actuator. It may be hidden under the sheathing.
The actuator can't be replaced directly from VW because technically there is no part number for it. I heard either boraparts or idparts found some replacements but you would have to contact them, if you find out, please post a follow up and post some pics to share what you learn.

The actuator should hold vac w/no leaks. IIRC you can adjust the BEW actuator but not sure. If you disconnect the rod from lever and the lever is still sticking you know there is problem inside vs. the actuator. However, you already know there's a problem with the actuator.

RE: boost leak test, not sure which EGR intercooler hose you are talking about but if the intake is sealed it should hold pressure. If a hose is off or depending on how far downstream you are testing, it may not hold pressure. If you blocked the MAF it should seal everything downstream. If you remove the oil cap you would also have to cap the CCV hose.
See less See more
I am adding your notes to the FAQ, many thanks! I haven't had to replace any smart sensors yet. On the BRM engine, it's high up on the engine. On the BEW it's low and exposed to salt and water which doesn't help anything.
1 - 4 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.