RhythmMachine

I have a 2009 ML320 Bluetec and have been getting occasional power loss issues, especially when towing, and especially up long hills. The trailer is about half of the stated towing capacity, and when the car is working normally it pulls like there's nothing behind it so I don't think it's an issue of what I'm towing, but every once in a while it just completely bogs down and seems to go into limp mode - keeps very low RPMs and has trouble maintaining speed. When it's happened, if I turn the car off and on again and start driving it goes back to normal... until it happens again. It may be that this has happened when I'm not towing, but I don't remember for sure - just know that it certainly has happened while towing. I don't know if it throws a CEL - I've bypassed the swirl flaps, so I have a perpetual CEL related to that (informing me that the flaps are stuck open), making it tough to know if any new codes would trigger that or not.

I was finally able to pull a code related to the issue, and it's P0299, which is for underboost conditions. From my research so far it appears that it may possibly be the back-pressure sensor (which, if I understand, can be contaminated from the DPF), a clogged DPF, the turbo actuator, or a leak somewhere in the turbo system. I have it booked to go into an indy shop next week, but thought if I can fix it myself in the meantime it would be even better.

I want to check for a turbo leak, most people seem to suggest starting with examining the intercooler hoses, but I'm not sure which ones those are (based on Sprinter forums for the same engine, they say the induction side, post-turbo is the most common culprit). I can find pictures of the hoses on Google, but haven't had any luck showing them in the context of the engine, so I'm not sure which ones I should be checking. Can anyone point me in the right direction? And any other suggestions for things I should be looking at?

Maj. Dundee

What module was this code P0299 stored in?

Are you using a scanner, if not, get one.

RhythmMachine

It's in the powertrain module based on Torque

Maj. Dundee

There are no "P" codes in any Bluetec module. This is why I asked you if you had a scanner which you obviously do not have.

RhythmMachine

Curious... I do have an attached ELM327 OBD2 adapter which shows the generated codes via Torque Pro on my phone, even though I don't have a MB-specific one, and I see many other posts about the P0299 error from other OM642 owners.

Either way, do you know which are the intercooler hoses? I would like to be able to check them, regardless of the code situation, even as a part of regular maintenance. Thanks!