MB-Rookie

Good morning all and thank you for your time in advance. Ok so I am working on a family members 2009 GL320 VIN: 4JGBF25E09A474072 (166,000 miles on the clock) and It has the check engine light on. She says it loses power and will barely go after 5 minutes of driving. I have an Autel 906TS Bluetooth scanner and used it to pull out 3 codes. The first code is 120B00- Component 'Y77/1 (Charge Pressure Positioner)' has Open Circuit. The Second is 159C00- An Internal fault exists in the component 'B5/1 (Charge Pressure Sensor)'. Finally the Third is 162400- An Internal fault exists in the component 'B76 (Fuel Filter water level sensor)'. Being that I wasn't exactly sure what the "charge pressure positioner" was, I went to my local Benz dealer and bought the charge pressure sensor(Part #: 006-153-99-28) and also the fuel filter, sensor and O-ring. I installed both and then cleared the codes. It drove beautifully for the first 5 mile test drive. I then decided to drive it again just to make sure everything was working properly and boom, check engine light. The positioner and pressure sensor codes came back. I did a little digging and found out that these OM642 engines have a problem with the internal positioner wires breaking loose at the solder joints due to vibration. I removed the positioner and separated the plastic cover from the metal backing. I noticed that it was not the factory Hella brand positioner and that it was much cleaner that any surrounding component of the engine. I'm assuming it's a cheap Ebay unit. I did not find any broken wires inside the unit so I put it back on and decided to run an "Active Test" with my scanner. During the test the Ebay positioner did not sweep through the 10% and 90% function test. I have a friend who has a diesel repair shop and by some stroke of luck he had a used positioner that came off of a seized 2012 3.0l 2500 Mercedes Sprinter Van. I swapped the Ebay unit with the used unit and viola, it passes the sweep test. It also cycles with key on like it is supposed to. I cleared the codes again and it drove beautifully for the second 5 mile test drive and again, the CEL came back upon the second startup. I scanned the computer again and it only has the 159C00 code for the pressure sensor. I find it hard to believe that the brand new Genuine Mercedes-Benz sensor is bad. Especially since it had the same exact code with the old sensor. At this point I decided to inspect and leak test the charge side of the turbo system but only found the typical oil residue in all of the charge pipes. I did not find any leaks after spraying soapy water on all charge hoses with engine running. I even removed the pressure sensor to see if there was any obstruction. All good there. No broken wires to the sensor either. I scanned the vehicle computer again and got into the "Live Data" section and found that the pressure measurement at idle is only .1 PSI over the set amount(13.6 PSI- 14.5 PSI) This vehicle measures 14.6 PSI at idle. I took the car on a test drive while having the scanner hooked up and I had a max Boost Pressure of 39 PSI!!! Let me tell you it had all the power!!! I am sure the scanner is lying to me or the sensor is lying to the scanner because you would think the head gaskets would blow at that pressure. Anyway, at this point the check engine light is on for the pressure sensor and I am not sure where to go at this point. Seems like the charge pressure is off and it's over boosting. Any help would be much appreciated. Again I hope you all have a great day!!!

MJ50

moved to X164 forum...