kevins_garage

I have a 2006 C230 that has around 26,000 miles on it currently. A few weeks ago, my doors began spontaneously unlocking while driving around.

I took it to a local dealer and they were unable to duplicate the problem. They said they found no codes and that the crash sensor and door sensors were not the problem. Just the doors were unlocking - no lights or other warnings came on when the doors unlocked.

I wasn't sure what was causing it, so I started searching and found one or two obscure references online. The one that was most intriguing was that this happened to others before that had something in their trunk. I folded down the driver side rear seat, started up the car, sat in the passenger side rear seat, and with the doors closed and locked, I began tapping my hand around the trunk area by the driver side SAM (fuse/relay block). Sure enough after a couple taps, the door locks popped right open. I locked them and tried again. Yep, they unlocked again. One more time just to make sure. Every time I tapped the SAM, the doors unlocked.

Apparently, when I had stuff in my trunk that slid around and hit the SAM, it was doing the same thing - causing the door locks to intermittently and spontaneously unlock while driving.

Know, does anyone have any idea on why this does this? Is it a known issue that I will just have to deal with, or do you think it is a defective SAM, or maybe a loose connection? I can't get it back to the dealer for a couple weeks. If it for some reason this is just the way this is going to be, I certainly don't want to waste the time taking it back to the dealer.

Saprissa

take it to the dealer, and repeat that same trunk/SAM scenario.

MB may not even know about that "bonus feature".

kevins_garage

I do want to take it in AGAIN, but only IF I can confirm that this is truly an isolated problem with my vehicle that can be corrected by replacing the SAM in my vehicle or finding the real problem causing this. I saw a few other posts about similar problems others have had with various years of C's, so I am finding it hard to believe that I am some kind of genius that single handedly figured this "bonus feature" out, and that it only happens with my C.

In other words, if this is just what is going to happen, even with a new SAM, I'd rather save myself the time and hassle of being without my vehicle for 2 days in service, and just do my best to minimize the circumstances that cause the problem to happen in the first place (now that I know what is causing it). Kind of like the old joke - a guy goes to the doctor and complains that it hurts when he puts his arm over his head. So the doctor tells the man not to put his arm over his head.

e1000

well, if it was me, i'd be wondering what else is being messed up by the faulty rear SAM.....

kevins_garage

Apparently nothing. It has already been in once and there were no codes - no nothing.

Hence the reason I am trying to take whatever reasonable steps I can to verify if this is a real problem (i.e. defective SAM?), or if this is just the way it was designed (i.e. possibly the impact on the SAM causes the door lock relay to bounce and unlock the doors and that's just the way it's going to be?)

I have a week or so to see what I can find out before I will have the time to get it back into the dealer. Unfortunately, the dealers near me are only open M-F 8-5 and I leave for week way before that and don't get home until way after. I don't want to drop it off after hours only to waste another 2 days because the tech/s couldn't duplicate the problem on their own or just to have it turn out that the doors will always unlock if the SAM is impacted. [sigh]

yeuchau

weird, first time I heard this.
but yah, I would just take it in again and repeat that same trunk/SAM scenario

QQQ

dumb question - what is SAM and what is it for?

alymo

it happened to me once before, it never happened again but now that i think about it i did have some loose stuff in the trunk so it makes sense,my SAM is brand new so i think it's just a problem with the design or something.

baodovvn

yea this happens to me randomly too. Like 2-3 times a month.

Rareamg

I don' know what SAM is either but I experience the same issue.

Saprissa

just a hunch....

but I would type in the letters: S A M
into the "Search" function...

it's amazing what you might find !

Rareamg

WOW.. thanks for the great tip!

Saprissa

it worked for me:

SAM = Signal Acquisition/Activation Module

Faulty front and rear SAM units on W203 C-class Mercedes sometimes cause lights failing/staying on and door windows/locks not working.


Carlos

Saprissa@aol.com

Rareamg

your the man!

kevins_garage

Sorry for not posting a follow up in a while, but apparently I beetched and complained enough about this issue that MBUSA has now issued a TSB or other notification to dealers abotu this issue.

MBUSA claims it is due to loose items in the trunk banging into the SAM on the drver side rear of the trunk and causing it to "think" there has been an accident, thereby signalling all the doors to unlock. What an effin joke!

Their suggestion to me was to secure anything in my trunk so it isn't allowed to move around. Whatever? Last I checked, there weren't any tie downs or anything else to secure much of anything.

If you want to duplicate it yourself, open the trunk, start your car and get out, closing all doors. Flip the lock on the decklid so the car thinks the trunk is locked, then hit the area in the trunk where the SAM is 2-3 times or so. You don't have to punch it hard, but it does need a pretty good tap. The locks opened everytime I did that.

C230 Sport Coup

I had this problem, but they replaced the door switches, the ones that make the lights go on when you open the door.
Then again, my car has had just about every electronic module,
harness, sensor, and wire replaced under warranty.
Stick it to the man! Errr...the dealer.
Now I seem to have a reliable vehicle (fingers crossed)
with the exception of the coil packs, which is why I keep a spare in the car.

120K miles.
I'd post my repair history but I'd be dead by the time I finished typing.
Get EVERYTHING you can under warranty. You have a 1st year car in the sense of the new 6 banger.

aolsen

Got in my 2003 C230 Sedan, and the door open indicator came on, the rear left door was open. I reach back, close it, and it opens again, all by itself. The door open indicator kept coming on and the door opened while I was driving. It didn't fly open, but I'm afraid of that happening lol. After restarting the car it didn't occur, but I wonder what caused that.

Jack_2001C240

My C240's doors unlocked by themselves while driving just as the original poster described about 2 weeks ago for the first time, after I hit a large depression in the road due to the asphalt settling after the electric utility did work under the street. This thread describing how the SAM reacts to large sudden impacts of force answers my question of why this happened.

acr2001

Yep, there is a crash sensor in the rear SAM. The normal behavior is supposed to be that during an impact that sensor unlocks the doors, turns on the interior lighting (not sure if this is only at night). And turns on the hazard lights. I find it strange that only the doors are unlocking. Maybe there is a sensor in the front sam for the hazards and interior lighting?!

pogijeffrey

yo!!! i had that same exact problem happen to me. it stopped doing after i took my car in for srs light problem along with seatbelt warning that kept flashing as if someone was sitting on my passenger side. as soon as i slowed down even when i was close to home that doors would unlock right there and then. i explained it to the dealership and they thought i was crazy. but it stopped doing it.