Hi, not sure if this is the correct place to post but I have a 2007 Jeep Grand Cherokee with the OM642 Non-DEF. Hard to find jeep specific diesel info so hope to find help with the Mercedes forums.

Anyways, having a very intermittent issue with no boost on key on. Can drive the car for a week at a time sometimes no issues, will randomly start one day and go to drive off and instant limp mode/no boost. Shut off for 5 mins and restart and no issues again. No codes other than underboost once in limp mode. Replaced actuator with $300 “rebuilt” and actuator would go too high. Replaced that with $50 amazon and now runs and drives perfect other than this random no boost issue. Looking to see possible causes before I either throw a bunch of money at it or get rid of it. TIA.

Edit 1 -

Thank you for all the replies, just wanted to update what had been done before. Turbo was replaced with rebuilt unit and actuator with that $300 “rebuild” I mentioned earlier as the original turbo linkage was stuck and killed actuator as well. New turbo moves freely and now with amazon actuator runs and drives perfect 90% of the time except when it goes into limp mode. Boost meets targets no problem and drivability is good. EGR/swirl flaps are deleted and tuned out. When the issue happens actuator will not move at all after key cycle or using scan tool. Any other time using scan tool the actuator will go from 0-100% no issues anywhere. Also if anyone could provide a pin out or way to test voltage at connector to see if it is the issue that would be great. For now I am going to clean and check connector and also look for boost leaks although I have checked before and didn’t find anything.

 

Although my experience is limited to Mercedes brand, I would install the original actuator back to the turbo, especially because your fault code it's not related with any electrical component. More likely one of the intercooler hoses needs to be inspected as from where you see oily marks the needed pressure is waisted.

 

From my experience with these OM642 engines, this sounds like a classic case of a failing turbo control module or a wiring harness issue between the ECU and actuator. I've seen corroded pins in the turbo actuator connector cause this exact intermittent behavior, especially when the engine bay heats up and the metals expand. The fact that you're getting different behaviors with different actuators suggests there might be an underlying voltage reference issue from the ECU, or possibly a ground problem. Another often overlooked cause could be a hairline crack in the intercooler or boost pipes that opens up under load and heat - these can be nearly impossible to spot without a smoke test. The cheap Amazon actuator might be masking the real issue due to different calibration parameters.

I'd strongly recommend getting a proper scan with a scanner that can access all modules, particularly the ECM and TCM. I've been using the youcanic full system scanner more lately because it gives me Mercedes-specific parameters and live data streams that basic scanners miss. If you're using something basic like an Autel AL319, you're probably missing critical fault codes stored in other modules. The youcanic lets me see actual boost pressure, wastegate duty cycle, and actuator position in real-time, which is crucial for diagnosing these symptoms. Have you checked the actual voltage at the actuator connector while the issue is occurring? That would tell us a lot about what's really going on here.

 

Based on the symptoms you’ve described, here are some potential areas to investigate further:

1. **Intercooler Hoses and Connections**: As mentioned, it's important to inspect all intercooler hoses and connections for any signs of wear, cracks, or leaks. Any loss of pressure in the system can cause the turbo to go into limp mode.

2. **Turbocharger Actuator**: You've noted you've replaced the actuator multiple times. It’s crucial to ensure that the actuator is functioning properly and that it’s calibrated correctly. If you have the ability, using a scan tool to check actuator position might provide more insight.

3. **Vacuum Leaks**: Check for any vacuum leaks in the system. Since the actuator relies on vacuum, any leaks might cause inconsistent performance.

4. **Electrical Connections**: Examine the electrical connectors to the turbo actuator and any related sensors. A loose connection can lead to intermittent issues.

5. **Fault Codes**: Even if no codes are thrown during normal operation, consider connecting a diagnostic tool while driving. Some codes may only appear under specific conditions leading to limp mode.

6. **EGR System**: Sometimes, issues with the EGR valve can affect boost performance. Inspect for carbon build-up or malfunctions.

 

Intercooler system leaks are most common issue on those engines.
I don't know if Jeep is having the same plumbing, but the U-cross cut seals on the hoses needs to be replaced every few years.
Any intercooler leak will show as oily stain around, assuming you keep it clean.

 

I just want to talk about my experience with this.

I have the North American OM642 engine in my E Class sedan and I had the mysterious limp mode that would first happen under acceleration, and then few months later it would happen whenever it felt like happening. I don't remember the exact error code I got as this happened two years ago now, but I remember it had to do with loosing boost. This was an issue that was driving me absolutely nuts for almost an entire year. I even completely removed my exhaust manifold and chemically cleaned my DPF (diesel particulate filter) in the desperate hope that it would fix the problem because I started to think it was clogged and causing the turbo to loose boost.

Can you guess what the actual problem was?!

One of those large stiff rubber hoses that go between the turbo and the intercooler had a soft spot in it. It wasn't a cut, it wasn't cracked, it didn't split open. It just had an apricot sized soft spot in the hose that you could easily feel when you pushed on it with your finger. So what would happen is that once it reaches a certain level of boost, this soft spot would all of a sudden inflate like a balloon, this would cause the engine to suddenly loose boost, the computer would then freak out and shut the car off and out it in to limp home mode.

Since it wasn't an obvious crack, or a cut, or any break in the rubber intercooler air line, this thing drove me absolutely nuts for an entire year, before I found it!!!

I wrapped some duct tape around the soft spot on the hose, to prevent it from ballooning a da went on a test drive, I did a lot of hard acceleration driving and the car didn't die, it didn't limp-home mode, nothing. That was my problem!!! That temporary duct tape fix stayed there for another year (completely problem free) before I finally got around to buying a new intercooler hose.

Check all of your intercooler hoses, I GUARANTEE you that that's where your problem is. The hoses are very easy to access and see, but the leak can be hidden from you, so take them off and physically go trough each one looking for soft spots or tears.

I can't believe how simple the problem was and how it drove me absolutely crazy for an entire year before I found it. I was ready to blow the car up.

 

That's crazy! The loss of boost couldn't have lasted more than a few nanoseconds. But, you can't argue with success!