I just bought a 2006 ML500 with 80k mi. on it. It has an interesting problem with the auto door locks. Intermittently with the car running the doors unlock. That is with or without the auto door lock activated. Also with the ignition off once the doors are unlocked you can hear the actuators continue unlocking usually at somewhere around a 6 to 7 sec. interval. With the ignition off the doors stay locked, but driving, intermittently they will unlock and continue to try and unlock. This is not the machinegun effect where when you try lock the doors they rapidly unlock or won't lock.
The passenger back door locking mechanism is not functioning at this point at all with the auto door lock system.
I'm having a hard time locating what controls the auto door locks to try find what is sending the signal to unlock the doors or what might be telling the controller that it needs to unlock.

Any ideas would be greatly appreciated.

 

I have the same problem. Doors unlock sometimes while driving. I've heard this could be the sensor that locks the doors once you reach the 7 mph speed that auto locks the doors when first getting going. I haven't worried about it too much yet. Any other comments?

 

Mine was doing this for a while and it drove me nuts.

I don't have the doors autolock, so they are always unlocked while driving. I'd hear them try to unlock (as if someone was pressing the unlock button) and you'd hear a little click.

I changed the autolock setting to ON so the doors were now locking all the time. As I suspected, once in a while they'd actually unlock by themselves.

I can't figure out how I diagnosed which switch, but it ended up being a bad passenger side door lock switch. It's the one in the passenger door with the lock/unlock buttons.

Wasn't outrageously expensive ($50?) and very easy to replace.. but there's a trick!

Get a pair of needle nose pliers and cover the tips with tape so you don't scratch anything. With the truck off, press the lock AND unlock buttons and hold them down. See the thin sliver of plastic between the lock and unlock buttons? Grab and pull hard with needle nose. That's the 'handle' you grab to pull the switch out.

Mine had a ribbon cable going into it that was oxidizing and starting to turn a bit green at the end. Cleaned it with contact cleaner so the contacts were good. Installed new switch.

That was about 4 yrs ago and no problems since!

Again, I do have a copy of DAS so maybe I used that to figure out the bad switch.. can't remember. I don't remember using DAS though. I think one day I taped the unlock switch down on the drivers side and drove the truck. .and then it still randomly unlocked again.. which meant it HAD to be the passenger side. If I drove for a day and didn't hear anything, I would have replaced the drivers side instead.

Anyhow, it's most likely the switch!