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FIXITMAN
FIXITMAN, Master Technician
Category: Mercedes
Satisfied Customers: 17324
Experience:  ASE MASTER CERTIFIED, AA DEGREE DIESEL/AUTOMOTIVE
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I have a 2007 ML320 cdi with a p0234 fault code... after

Customer Question

I have a 2007 ML320 cdi with a p0234 fault code... after some research I'm trying to determine what is the most likely issue. I've seen replace complete turbo, replace actuator, egr plugged, etc
JA: Just to clarify, what's the exact code? And have you tried to reset it?
Customer: p0234 turbo overboost
JA: Are you fixing your ML320 yourself? What have you tried so far?
Customer: not necessarily, I've cleared the code but that's it... I'm trying to determine the best next step. I grew up in the repair business, but don't have extensive experience with diesels
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 9 months ago.
Category: Mercedes
Expert:  FIXITMAN replied 9 months ago.

Hello, my name is***** you tell me if the engine is lacking power or if there are any strange noises coming from the engine?

Customer: replied 9 months ago.
initially when you start it up the turbo works fine without any noticeable noise. However, after driving it a short distance it will go in to limp mode and the acceleration off the line is terrible.
Customer: replied 9 months ago.
Any insight?
Expert:  FIXITMAN replied 9 months ago.

Thank you. Does you scan tool read the boost sensor data?

Customer: replied 9 months ago.
No, but I can probably borrow one unless it needs to be a mb proprietary scanner
Expert:  FIXITMAN replied 9 months ago.

Some generic scan tools will read it. You need to see what the boost pressure sensor is doing when this occurs. If it drops to nothing then the sensor may be bad. If not then the turbo is the next most common failure.

Customer: replied 9 months ago.
The boost pressure sensor can cause an p0234 over boost dtc? And if the pressure sensor is reading properly do you only recommend a new turbo or have you had luck with remanufactured turbos? I've heard mixed results.
Expert:  FIXITMAN replied 9 months ago.

Re-manufactured turbos are about a 50/50 shot of them working well and lasting. As for the sensor, yes it can cause this if it is reading incorrectly.