Tigerstylin74

Hey all,

Here's the low-down. I recently bought an '08 ML320 CDI and it ran beautifully for the first two weeks and now it's acting up. First, there was a check engine light and it went into limp mode. I did a diagnostic check - DTC P0299, Underboost condition, so I replaced the fuel filter and erased the trouble code with the diagnostic tool to see if it would reset the limp mode... It didn't. Still had no power.

The next day I start it up and it's running really rough and died just pulling it out of the garage so I just limped it back in and now here I am.

Was it a mistake to clear the code? I just thought if the problem wasn't fixed that it would just show the check engine light again but now it's much worse.

Any ideas where I should start? I'm new to Mercedes and diesel at the same time so I'm biting off a lot here, I know, but I'm fairly mechanically inclined so I'm confident... I just need some help getting started.

Thanks, in advance, for any help offered.

Justin

Tigerstylin74

Ok, so it ended up being something really simple... As I started disassembling things to get to the turbo, I noticed some fuel on top of the filter and decided to start it to see if it was leaking. I started it and it ran perfectly at idle.
All I had done at that point was removed all of the air ducting around the turbo i.e. filters and housing, ducting to and from the turbo but the key was the sensors.
I assembled everything except the sensors and plugged them in one by one and located the problem... The MAP sensor on the housing of the driver side filter. It's on order. If I get it and it's not the solution, I'll report back.

Hope that helps someone.

OUZO Power

love it when someone finds an easy fix on their own and doesn't have to go to the dealer. Good luck.

Tigerstylin74

Well, unfortunately it's turning out to be something more.

The part came in today, I installed it but the car was still in limp mode. I disconnected the battery and let it sit for about an hour and reconnected but now the check engine light is back on and it drives with severe spurts. I'll have to get another diagnostic tool and see what it reads.

Any suggestions?

leeroytandy

you've probably found a solution by now.
Mine is bringing up the same code . but only goes into limp mode when push it to 160km/h.

Maj. Dundee

The code/s must be cleared.

Brent Makelki

Did this get resolved? I have the same issue/error. Was miss firing so put in fuel conditioner and better but still missing @2800 rpm but not under load. Next day ran fine in city then parked and now wont start (on XMAS eve-great). Fires for ~2sec then dies. Replaced fuel filter (and air filters-what a crazy design just to replace these!). OBD code P0299. Cleared code, still no change. Will try disconnecting the sensors. Suggestions?

Scott Robertson

Did you ever solve this?