P0234 Error Code Linked to Linkage?


Active member
... the P0234 code. ... I was able to clean and lubricate the turbo actuator linkage ... This cleared the P0234 code and restored normal turbo operation.
Checking and cleaning the turbo actuator linkage sounded like a good next step in my troubleshooting.

Trying to get in a quick ski trip last month, I did an oil/filters change, grabbed the dogs and only made it about half an hour out before going into Limp Home Mode (LHM). When I saw that the Intake Air Temperature Sensor (and everything around it) was covered in oil, I figured it had to be a split hose, so I replaced the sensor and the intercooler hose. But the old hose showed no signs of a leak and the LHM problem remained, producing a check engine light and P0234 code.

This morning, resolving to solve the problem, I spent most of the day trying to catalog all the possible causes of Limp Home Mode with a P0234 error code. Checking the easy things first, I grabbed a neighbor and had him press on the accelerator while I watched the turbo actuator linkage. Nothing.

Then I removed the heat shield and found that the actuator arm moved freely, and no wonder because the linkage was dangling below it. Assuming that it's supposed to be connected to something, I'm praying that's my entire problem.

Next stop, figure out where and how to reconnect that arm. Maybe we'll be able to get away for the Fourth of July after all. The fireworks around here make the dogs miserable.

Last edited:


Active member
Unfortunately, the bottom of actuator arm attaches to the actuator in a very tiny space. I can barely get a couple of fingers in there to try a push the arm back onto the pin. There's no way I'm going to be able to get a clip over the pin.

So, I'm hoping that the actuator can be removed by simply loosening the obvious bolts.

https://www.eldensengines.com/Otherstuff/Sprinter Turbo Fix/Sprinter Turbo Fix.html

Edit: Son of Sea Biscuit! That was not easy to remove. Had to get the turbo resonator out of the way and I had forgotten how hard those little 8E Torx bolts were to work with.

Off to the store tomorrow to get a new circlip, which will hopefully solve the problem.
Last edited:


Active member
Success! Took me most of yesterday afternoon and this morning, but I got the actuator out and went to AutoZone for some Dorman assorted circlips. Got it all back together and everything runs perfectly.

The moral of the story is that the P0234 error code can be triggered by a bunch of different things. And, it pays to lube up your turbo actuator linkage so the circlips don't get rusty and disintegrate. And, take Keith's advice literally. I should have focused on the turbo's functionality from the beginning.

A million thanks to Green Diesel Engineering, for the great tune and for their generous advice.


Without taking the time to organize them, I'm going to copy my P0234 troubleshooting notes below, on the chance that it might help someone else.

2006 Sprinter T1N 3500
2007 Winnebago View RV
GDE Tune
OBD11 Bluetooth Scan Tool (BAFX 34t5) and Torque
46,471 miles

Just prior to problems, did maintenance:
Oil change, oil filter, fuel filter, air filter, cabin air filter

Drove for 30 minutes highway speeds on a hot day, then went into Limp Home Mode, max speed 40 mph, seemed to rev okay with no load.

Check Engine Light, Fault code: [P0234]

From Keith at GDE:

P0234 is an over boost code.  You need to check the turbo to make sure it is functioning properly.  Clear the code and run it hard for a bit.  Does the code set in light load or heavy load driving?


Intake Air Temperature Sensor 2002-2014    $22.91  EPN: 651 153 00 28
 Dorman 904-097 Intercooler Outer Hose $46.49 OE Part #5120147AA
Old sensor was covered in oil - no apparent hose split

On hand to be replaced:
Dorman 904-303 Turbo Sound and Vibration Dampener $29.99

Unplugged Mass Air Flow Sensor and engine didn’t run exactly right but seemed to have close to normal power. MAFS didn’t look dirty, but cleaned with compressed air.

Next Steps:
Search forum for Error Code P0234

Check all hoses and install turbo resonator
Visual test of turbo actuator. Do before and after LHM kicks in.

Try to verify if you actually have abnormal boost pressure or not. Get connected to a diagnostic scan tool which can show boost values. That would be a DRBIII dealer scan tool with adapter card and cable, a DAD, or even a Scangauge II should work. An OBDII generic scan tool like most parts stores have will not.

Search on intake air sensor!!!!!!!!!!!!

Check hoses off of Mass Air Flow Sensor

See Write-Ups Section

Replace other hoses

Test Load and MAP

Crawl underneath the turbocharger and inspected the vacuum line feeding the turbo actuator, with no obvious signs of damage or disconnect.

Threads on Sprinter Forum:

Aqua Puttana - LHM limp home mode possible causes - Completely read and noted

Aqua Puttana - LHM Limp Home Mode Experiment

Aqua Puttana - Turbo Hoses Part #’s

Resonator replaced, still not right

Reset engine light?

2005 Low Boost Diagnostics
Engine Speed Diagnosing

Mass Air Flow Sensor

Service Manual

Codes Manual

Various Notes:

P0234 is "turbo boost limit exceeded" hinting that either the turbo is over-boosting or that the MAP sensor (finally) is misbehaving.

removed the vane actuator and assured it was clean and free from any rust or seizing.

For the past 2 years or better I have been suffering from the occasional limp mode (loss of turbo) syndrome. I replaced every sensor possible, no fix was had. Even my new engine and transmission from Dr. A did not solve the problem. One of Andy's final thoughts was to by-pass the converters and muffler. So yesterday morning before heading out on a 300 mile leg of my current trip I separated the exhaust pipe just before the converters. A bit noisy but NO MORE LIMP MODE. Now I just have to find a muffler shop that will put in a temporary straight pipe. Thank you Dr. A! New engine runs GREAT!

You might have an excess accumulation of oil in the intercooler, that's sending blurps of oil messing up the MAP sensor.
(i use the IAT as my test since it's "just a squeeze" to remove)

Yeah, people have reported that a bad or disconnected IAT will make the ECU crazy and it will go into a LHM where it shuts off the turbo. Never happened to me, but I've read it here before. Same with the ambient air temp sensor (behind front license plate)

If restart restores power, (YES) the computer was involved in limited the power.
If limited to one gear (NO) then transmission problems.

Inexpensive code readers don’t show all codes or offer accurate descriptions.

Turns out the Intake Air Sensor can also cause turbo vane lockout. Both those failures may set Mass Air codes and not necessarily set DTC's specifically pointing to the failed part.

Turbo Boost Pressures
Turbo resonator failure - would that cause Overboost fault?
Splits in turbo outlet hoses, cracked Charge Air Cooler
Electrical turbo blade positioner on 2006 OM647 engine
EGR problems (Do I have EGR delete with the GDE tune?)

Probably not a transmission problem, but should check and do maintenance.
Overheated fuel possible - not a DIY.
Crankshaft position sensor - unlikely.
Accelerator Pedal - would fix speed at 1100 RPM’s
Throttle Plate Frozen - below freezing temperatures only
Low Fuel Pressure

Ambient Air Temperature Sensor - Check on Dashboard

The EGR Back Pressure Sensor
The EGR back pressure sensor is located in the exhaust stream next to the EGR bypass valve. The sensor determines the exhaust pressure before the catalytic converter. The ECM uses the EGR back pressure sensor for engine protection and exhaust gas turbocharger protection.

To prevent damage to the turbocharger from overheating and/or overspeeding, the ECM monitors the exhaust pressure upstream of the turbocharger. At high exhaust backpressures, the speed of the turbocharger drops and consequently the boost pressure drops. The ECM adjusts the guide vanes in the turbocharger to regulate the boost pressure.

WARNING: If the exhaust back pressure is too high, the ECM switches to limp-in mode to protect the turbocharger. The limp-in mode can only be reset by restarting the engine. 

If the boost pressure sensor fails, the ECM records a DTC into memory and continues to operate the engine in one of the three limp-in modes. When the ECM is operating in this mode, a loss of power will be present, as if the turbocharger was not operating. The best method for diagnosing faults with the boost pressure sensor is with a diagnostic scan tool.
Refer to On-Board Diagnostics in Emissions Control System for a list of Diagnostic Trouble Codes (DTC's) for certain fuel system components.

Underboost condition
Check turbo plumbing (split in hose)

(Compare boost air temp sensor to ambient air temp??)

The codes for overboost and underboost are not always clear.
What device was used to get the "P0234 turbo/super charger 
overboost condition" code?
If this was on a DAD unit or the MB SDS system, then you may 
have actually had an overboost "spike" that unseated the O ring
and caused an actual underboost/LHM.
If this code was developed on a generic scan tool (ScanGauge II/
UltraGauge EM/DashDAQ) then the overboost condition was probably
just a spike that caused something in the turbo plumbing to leak.
ECM sensed this and put you in LHM.
Since you found the missing bolt on the TR, and have corrected that
issue, you are probably good to go.
Overboost/Underboost codes often come in pairs and it's not always
clear which triggered the LHM.
LHM is definitely an underboost condition, but is there to prevent 
damage to the turbo and it's plumbing in the event that boost is
not being controlled within the factory programmed parameters.

What is the MAP pressure? Its pretty likely that you have an air leak somewhere in the lines from the airfilter enclosure, thru the MAF, thru the Turbo, thru the Intercooler and up to the air intake - a leak anywhere will cause what you are seeing. You can have a leak between the MAF and the turbo - plenty of turbo pressure, but the MAF air flow reading does not match the rest of the system performance, and the ECU will go into limp mode.

The MAF could be dirty too - its easy to clean (get right spray cleaner specifically for MAF sensors). Removal is easy (I don't even remove the connector), then to put it back, I use a bit of grease on the rubber O ring that the MAF slides into on the air cleaner assembly - and its back in.


A sticky turbo actuator link can cause it.

Although some people apply the term when referring to Sprinter turbos, there is no waste gate in the design. vic

no i have not. i am assuming there is a variable vane actuator and a separate waste gate actuator?

ok, so what i have tested is the variable vanes it's self by disconnecting the servo arm and moving the lever with my finger. my next step is to check the servo and it's arm

As AP suggests, there is no other "waste gate" or turbo boost regulating device (besides the
variable vanes and the electronic vane controller/actuator) on your 2006 OM-647 Sprinter engine.
If the electronic actuator is working correctly, you can see the bell crank arm on the front side of the reat (hot) turbo chamber rotating as the actuator extends and retracts.
Have someone sit in your drivers seat and rev the engine to < 2500 RPMS.
You will see the actuator link extend and rotate the bell crank which in turn rotates the vane
ring inside the turbocharger.
If you see no movement of the actuator link and bell crank, you probably need a new turbo vane actuator.
They are available seperately, but you have to look a bit.
Most shops (practically all dealers) will try to sell you a complete new turbo with actuator, claiming that they do not come as seperate parts.
The complete turbo unit w actuator is very expensive.
The actuator by itself....not so much.
Might want to invest in a ScanGauge II or similar so you can see what the boost actually is and watch for underboost or overboost in real time.
Hope this helps,

with sensor failure its import to check wiring for breakage/wear etc first.

Partially clogged air filter caused sudden loss of power above 3000rpm at random times.

My trusty Indy Euro mechanic after hearing my story recommended I first "hard reset" the vans computer before bringing it to him. This "hard reset" consisted of detaching the positive and negative battery cables and leaving them connected to each other for at least ten minutes. This seems to have helped somewhat, but hasn't totally alleviate the slow speed stall.
Last edited:

Top Bottom