m1kefries

I've owned an '07 CDI since new and recently have been having issues in the morning when it is cold, 5 degrees fahrenheit. After waiting for the glow plug light to go out I start the ML and let it warm up for a few minutes. Put the truck in gear and motor on down the road, but it is in "Limp Mode". It won't respond to the accelerator pedal and will only go to about 2k on the tach. This has happened several times recently with no check engine light. After driving for several miles I'll pull over and shut off the engine and wait for a couple of minutes. Crank it up and all seems to be ok.

This weekend I was in Northeast PA and getting ready to tow my 7x14' trailer home to Virginia Beach and the dreaded "Limp Mode" reared its ugly head again, but this was the first time I had a check engine light. I took it to the closest dealer and they squeezed me in. The computer had two codes, one for fuel pressure differential, and another for the Diesel Particulate Filter. They ran a bunch of tests and updated the ECU software. By this time the temperature outside had gone up to about 27f and they could not recreate the issue and that the tests of the individual components was fine.

This morning I had the trailer all hooked up and ready to roll at 7:00am and 5f. Warmed up the truck for about 20 minutes while loading gear and hit the road. Sure enough it was in "Limp mode" again, but no check engine light. I drove the back roads to the next town and stopped for breakfast to give it a rest. By the time we got back on the road the temp had risen to about 18f and all seemed to be ok again. Ran 8 hours back home without any further issues.

I've owned the vehicle since new and made this trip every year multiple times in the winter without any issues. It seems like some sensor is getting marginal, just not sure what to look for. I've got 78k miles on the clock and just wondering if anyone else has seen this issue or one similar? The service adviser said he doesn't see many diesels so this is not a familiar issue to him. Any input would be appreciated.

Vernl

You might live in an area that does not have winter diesel and you have a bit of gelling going on.

jqMLCDI

I use "Power Service" diesel fuel supplement here in Ontario, Canada its helps with cold weather starts and boots the octane .... it also has slickdiesel additive....give it a try

dgiturbo

I had this a long time ago in 07. The fix I think was to either replace the "Upstream air sensor" or some fuel pressure thing. Give me a few and I will check the invoice.

I do remember talking with the tech and he advised that these diesel can make serious power, enough to completly destroy the 7Gtronic transmission, and the secrect to the power is raised fuel pressure. So the engineers installed a failsafe program "Limp home" to limit the vehicle to +- 2000 RPMs and second or third gear if it detects fuel pressure over a set amount.

Now that I think about it, this issue occured during winter also.

mack1ro

DPF Sensor.Had the same problem.