ML 320 permanent limp mode

[jbar24]

I have a 2000 ML320.

A couple of months ago I was coming into town off a highway drive and boom, limp mode. Had no idea what was happening at first. When I turned the car off and on it was fine. Took it into the mechanic to read the codes and the first thing that came up was fluid leaking from the pan gasket and from an oil cooler fitting. He replaced the transmission filter and pan gasket and added fluid. The car worked fine for 24 hours and then limp mode again.

Back to the mechanic who checked the EGR for a clogged passage - he cleaned out the EGR tube. The vacuum hose was soft and cracked, so he replaced that and the coolant expansion tank. This worked fine for a few days, then the same thing - coming in off a highway drive and into limp mode. Back into the mechanic who said that there was fluid on the conductor plate so he just replaced that. Now the mechanic can’t get it out of limp mode and says he has no idea what is going on and we’re basically out of luck - that we’ll have the replace the whole transmission. So, we’ve spent almost $2000 to have a non-functional car, and frankly at this point it isn’t even worth replacing the transmission.

I am hoping that someone has another idea as to what could be wrong with it? I have read through all of the boards extensively - in fact I printed up two pages to take to the mechanic. At a loss.

Also - am I obliged to pay all of this amount for a car that is not fixed? We’ve already paid the first two bills ($1000) and who knows what this last one will be (we haven’t picked up the car yet). I honestly don’t think the mechanic was trying to rip us off but at the same time I can’t see paying $2000 to get my car fixed and now it is absolutely 100% broken.

Thank you for your help.

[ILUVMILS]

Tow your car out of there ASAP and bring it someplace with the tools and knowledge to fix it.

Paying him for fixing the fluid leak seems reasonable but I wouldn't pay for anything else.

[Zulfiqar]

tow your car out of there as mentioned above, it seems that the mechanic is not experienced in mercedes benz repair.

By limp mode Im believing you are trying to say that the transmission gets stuck in 2nd gear at full pressure engagement (slam into gear). To get the transmission out of this mode there is deeper level reset directly commanded to the transmission computer, it is not like a GM/Ford etc.

Such limp mode is invoked by the transmission computer to prevent the transmission from burning itself up (this transmission handles quite a lot of torque and is very keenly watched/read by the transmission computer to apply/release a certain gear ratio.

This repair usually involves replacing the conductor plate in the transmission as 90% of the times the speed sensors in the plate become faulty over time. In other repairs it has been seen sometimes that the wiring on the round plug going into the transmission has cooked and flaked off and is either not making contact or is shorting to each other.

A good mechanic can scope out the speed sensors to see any anomaly in their testing and start finding the actual fault.

In some cases the transmission computer gets flooded with oil as it leaks past the connector O rings and is wicked up into the wiring harness finally being dumped into the computer case. It can be cleaned out with 2 cans of contact cleaner and about half a roll of towels.

The information you have provided is somewhat incomplete at the moment though - the above is written because you mention limp home mode and then mention that the mechanic wants to put in a new transmission.

[Mia73]

I just had my conductor plate replaced on my ml430 runs and shifts great! Now it's leaking fluid, tranny fluid, did not do this before. I'm taking it back to the shop, but I was wondering if anyone knows what it could be?

[mauiloving]

Hey, jbar24!!!!

I was having similar limp mode issues with my '02 ML320. Mia 73 is offering good advice and a good place to start. There are multiple problems that can cause this issue.

Most of the people that I asked for help advised to replace the conductor plate, which I did, but the limp mode issue remained. Next, there was a code for the traction control module. I ordered a used one from eBay and sure enough, that was the issue causing limp mode.

Scan your ML and see what codes pop up. If there is a code for the Traction Control Module, then I would say start there. Regardless... one day you'll want to replace the conductor plate. That's been the only flaw in that transmission.

[alsevi]

As mentioned, look at the transmission electrical wire seal socket at the rear of the transmission. Fluid migrates up the wires and causes problems. An inexpensive part. I had your problem intermittently, progressively worse, and now no limp mode after socket change.