mverboom

Anybody have the problem the doors spontaneously unlock when driving? I've had it happen a few times now. I've got the automatic doorlock on when the car gets roling, and under some circumstances it unlocks when driving. I've just had it happen two times when driving back from dinner.

The only thing I could find that might be a clue is a diag code in de command diag menu. It's code B1795. Probably a bodywork code, could have something to do with the doorlocks. It's got a count of 5. Unfortunatly I can't find anything on the web about the SAE diag codes.

Anybody have more info?

Thanks,

Mark

Fuzzo

someone else on this forum reported the same problem? was it you??

what year is your car?

WyattEarp

It's happened to me twice. I've not done anything about it.

DtS

The only time the doors are SUPPOSED to open (without pressing the lock/unlock button or opening the door from inside...) is in case of an accident. The door locks are connected to some kind of a crash-sensor. I recommend that you have it checked as soon as possible (imagine there is something wrong with the crash-sensor and the airbag starts inflating during normal highway driving!)

mbtech208

The crash sensor doesn't directly unlock the doors. A crash signal is transmitted from the sensor to the SRS control unit, which then transmits data over the CAN data lines. This information goes to the door control modules (unlock doors), front and rear Signal Acquisistion Modules (turn on hazard lights), Overhead Control Panel (turn on dome light), ME-SFI control unit (cut fuel pump and open all injectors). I don't know whats causing your mysterious unlocking, but this is what happens in a crash anyways. So don't worry about your airbags deploying unexpectedly.

mverboom

It wasn't me afaik.

Quote:

what year is your car?

It's a 2001 C270CDI.

Mark

mverboom

I've had it checked out by the dealer when the car went for its first service. But the couldn't find anything .

The only clue I could find myself was the diag code in the comand system.

I'll go to the dealers first thing on monday and see if they can check it out again.

It's weird.

Mark

Richard

The diag codes you see in COMAND are faults registered by COMAND not by other modules on the car (i.e its not a magic way of interrogating the whole car).

B1795 is "Fault in CAN communication with component N73 (EIS control module)"

EIS is the electronic ignition switch. I dont know why COMAND is communicating with the EIS, but i'd imagine its so COMAND knows whether the ignition is on or off. I also dont know anything about whether the EIS talks to the control unit that deals with the doors.

Pehaps MBtech may know more. I know (stuff) about COMAND from trial and error and playing with StarDiag at a dealer. I printed of the full set of COMAND fault codes, so thats how I know what the error means

mverboom

Ah, ok, that explains a lot Thanks, I though the diag codes in comand could also be for other parts in the car.

Mark

mbtech208

The EIS is very important. It acts as the gateway for nearly all the CAN communication throughout the whole car. Your problem may very well be a bad EIS, but without checking the car out myself, its hard to say for sure. The only similar experience I've had was an SLK230 that would unlock the doors while driving on turns. The dome light would come on as well. I finally figured out that the passenger-side door was misadjusted, and on left turns, it would move outward just far enough to trip the dome light switch and unlock the doors.

VoyagerDude

I guess I was the one that brought this up a while ago:

Door auto-unlock???

mverboom

did you ever get it resolved?

Mark

VoyagerDude

Nope.
It only happened once.
Maybe it was related to low batter too

mverboom

The car has been to the dealer. They tried to find the cause of the problem, but after about 6 hours of searching couldn't find anything . They asked mercedes if it was a know problem, but they have nothing on record.

They're going to attempt to fix the problem by replacing parts that might be the cause. First thing they're going to replace is some kind of switchbox (forgot the name). Unfortunatly it's in backorder, so maybe it's going to be installed this week. Hopefully it will fix the problem.

Mark

DtS

Hope they find a solution for your problem Mark.
It looks like there are alot of electrical glitches in our cars... I can accept that as long as I can get it fixed. What scares me a little is that there seems to be many service places that don't know how to fix stuff. I mean, ok, this cars are packed with quite sophisticated technology, but someone once constructed it and built it, therefore it should be possible to fix anything...

Good luck!

mverboom

What I've seen up till now is that problems can be fixed easily when there is a fault code in the system. As soon as there is a problem without a code, you've got a real problem...

And I have two of those at the moment . First the doorlocks, and sinds tuesday the engine sometimes looses power. Cause undetermined

Mark

dswildfire

so i was driving all around the valley today, looking for washer fluid for my trip to mammoth, and the doors unlocked by themselves. no reason. i locked them. about 5 minutes later they did it again. i figured if i turn the car off and let it sit for awhile, all will be well. nope. went to SavOn a few hours later, and on the way back it did it again. anybody have a fix that doesn't involve taking it to the dealer?

moomeh

a month back i had a problem where the doors would not lock. i did not see a dip in the road and the car took a huge plunge into the pavement. the doors unlocked. i suppose the computer thought i was in sort of accident and unlocked the doors for evacuation. anyway, i could not lock the doors. however, the next morning i doors unlocking and locking became functional again.

yours is the opposite. mine was related with the impact. yours seem to have no cause due to wreckless driving. IMO, wait and see the next day if the car has problems staying locked. I was about to rush to the dealer the next day when the car regained functionality of the locking/unlocking feature.

dswildfire

thanks moomeh, i'll wait and see.

Matt230K

I had this problem several times a few months ago. I couldn't pinpoint exactly when it was doing it. And then it stopped doing it, so I stopped thinking about it.

LiquidSmile

Mine did that as well... I have to go in for my fist A service this week, so I will have them check it and get back to you on what they say.

hobie

Yeah, me, too. Neither rhyme nor reason, once every few months. Never bothered to mention it to service.

firstkill

I use to have this problem also.. usually when i make some quick turns with a heavy object in the trunk. If the item in the trunk bounces around and hits the sides ( near the fuse box ) it will unlock the doors every time.


fk

dswildfire

well, several weeks now, and no problem. i guess it must have been the bottle of wiper fluid in the trunk, hitting the fuse box. thanx for the replies.

EKY

I did a search and didn't really find anything regarding my problem. As I was merging onto the highway, as soon as I reached 50mph, the doors all unlocked. It really freaked me out. I tried to resimulate this problem, but i couldn't. Has anyone else had this issue?