DPDISXR4Ti

Vehicle is a 2005 E350 4Matic Wagon with ~175K miles. Had some weird issues - possibly went into limp mode briefly - self-corrected and got home. Pulled a P2602 code, "Supply voltage to solenoid valve is faulty".

I'm reading about earlier cars having an issue with oil getting wicked up to the TCM via the harness. Has that been an issue with the W211's also? If so, seems that determining whether the TCM, Conductor plate, or solenoid(s) have failed can be a challenge.

Thoughts?

Plutoe

Find someone with a good MB DAS system and knows how to use. You have built in tests to localize your issue!

AUTOdidact

This may be caused by the adapter plug (has been redesigned several times and should be renewed at every fluid change anyway) or simply a weak battery.

Go the easy way and check the battery first

DPDISXR4Ti

Both batteries are fairly new - especially the aux - so I doubt it's that. Unless the R&R of the aux battery is what triggered the code!

I've seen the adapter plug w/ the two O-rings, p/n A2035400253. But it's been suggested to me that's only a fix for external leaks, not the issue of the fluid wicking up to the TCM via the harness. Yes, no, maybe???

DPDISXR4Ti

Fair advise. I've previously spent time on this car chasing SRS issues that were beyond my pay grade. I won't go down that rabbit hole again.

AUTOdidact

The outer o-ring seals to the transmission housing (and prevents leaking to the outside), the inner to the conductor plate - this prevents oil leaking through the adapter into the plug.

It's a 10-minute-fix, not necessary to drain the oil/ remove the pan for this.

DPDISXR4Ti

Okay, sounds like it's a good thing to do along with taking a look at the TCM to see if any oil has climbed up there.