Not sure if this thread is dead, but I've been getting the same issue, except mine is coming on and off. I've been noticing that it seems to come back more consistently on hot days. The fact that it turns on and off leads me to believe it's an electrical and not mechanical issue. I ohm'd out the connections to the main relay and those are good, tried to tighten up the connectors on the solenoids but can't seem to get the terminals out. I will be revisiting this when I have some more time.
Some of you may be wondering why i'm doing this instead of going straight to the solenoid, and the fact is that I already replaced one and the code has returned, plus it seems a bit odd to me that two of them would trigger at the same time.
If anyone would like to try tightening the connectors and report back to me it seems like this may become a common issue as these cars gain some more miles. I spent some time working on Mercedes and they had a similar issue with older cars.