Mercedes-Benz Forum banner

1 - 20 of 21 Posts

·
Registered
Joined
·
473 Posts
Discussion Starter #1
This has been bugging me for some time, SRS light is ON and the fault code is Child seat recognition. Can't get rid of it. What is this?

Why would 2-seater even have child seat recognition? How can I get rid of this "feature"? Can the control module be re-programed with DAS to ignore this?
 

Attachments

·
Registered
Joined
·
98 Posts
There is a sensor mat built into the passenger seat bottom that detects whether the seat is occupied or not - in order to prevent firing the airbag in case of a "light" child on the seat.
I guess you can override it mechanically but you'd certainly lose your safety certificate for the car if authorities find out, also in case of an accident it is quite a bad idea because you don't get the airbag for the passenger so would not suggest to do it. You can first check the connections to the mat, perhaps it is a simple plug that is broken or open, otherwise you'd need to replace that mat, it should be available with Mercedes - depending on the model year it might be one piece with the seat heater etc so can be a little complicated, I'd guess the max cost will be approx 600$ with Mercedes.

Furthermore there is an electronic sensor in the seat that connects with an electronic sender that is in the base of an original MB children seat. This will switch the airbag off as well, even if the weight of the children seat (and the kid as well) might be higher than the threshold for the upper sensor. Anyways the effect will be that your passenger does not have an airbag.
 

·
Outstanding Contributor
Joined
·
4,109 Posts
How can I get rid of this "feature"? Can the control module be re-programed with DAS to ignore this?
In 12 years of owning a 2003 SL one of the very few problems I have had is with the same B48 fault described here. Since the sensor works in conjunction with a baby seat I do not possess, spending $400 on a replacement sensor seemed silly. I used Star Diagnosis (specifically, DAS Developer Mode) to remove the sensor from the SRS system's coding, and the fault disappeared. It's not possible to do that on an R129.

If my R129 had this problem, I would remove the instrument cluster bulb which illuminates the SRS fault indicator.
 

·
Registered
Joined
·
944 Posts
..If my R129 had this problem, I would remove the instrument cluster bulb which illuminates the SRS fault indicator.
I would agree with Bob on this one. And if your local regulations require inspection, where SRS light has to come one for few seconds with ignition on, then disappear, on my little brother's car, I've used this simple adjustable timer https://www.ebay.com/itm/12V-5A-Delay-Timer-Switch-Adjustable-Relay-module-0-to-1000-Seconds/282500579171?hash=item41c658bf63:m:msuoZ98clhtYo6wNHpweOjQ:sc:USPSFirstClass!22508!US!-1&var=581656520858 wired to an independent bulb attached to the factory SRS bulb location in the cluster, so it looks like "it works" as intended, passes inspections and does not annoy by staying on all the time.

There are always options of replacing the sensor $$$

Regards,
D
 

·
Registered
Joined
·
473 Posts
Discussion Starter #5
In 12 years of owning a 2003 SL one of the very few problems I have had is with the same B48 fault described here. Since the sensor works in conjunction with a baby seat I do not possess, spending $400 on a replacement sensor seemed silly. I used Star Diagnosis (specifically, DAS Developer Mode) to remove the sensor from the SRS system's coding, and the fault disappeared. It's not possible to do that on an R129.

If my R129 had this problem, I would remove the instrument cluster bulb which illuminates the SRS fault indicator.
There is a "special functions" option in control unit programing. I requires full 17-digit vin # and some validation code after that, I'm curious what could be done there. Has anybody tried that?

But OK, as it is now, with child seat recognition fault code present… is passenger Air Bag disabled no matter who is in that seat? And if I remove interment cluster bulb, that air bag will still remain disabled right?
 

·
Registered
Joined
·
98 Posts
Yes it will remain disabled - very dangerous for your passenger and a potential crime if an accident happens or if you ever sell it with this manipulation - not advised
 

·
Outstanding Contributor
Joined
·
4,109 Posts
...with child seat recognition fault code present… is passenger Air Bag disabled no matter who is in that seat?
Intuitively, if the SRS controller were going to disable the passenger air bag, then it would illuminate the air bag "off" LED. If the LED is off, then I would expect the air bag to be fully operational.

...a potential crime if an accident happens or if you ever sell it with this manipulation...
I believe the notion that someone in the U.S. would have legal exposure to removing an instrument cluster warning lamp is silly. A driver using a Mercedes "Baby Seat" has two warning indications that something is wrong with SRS prior to starting the engine: (1) the SRS lamp does not illuminate when the key is turned to position I, and (2) the air bag "off" LED is off. Nevertheless, if I had legal concerns then a simple alternative to removing the bulb is to install a non-working bulb.
 

·
Registered
Joined
·
473 Posts
Discussion Starter #8
Yes it will remain disabled - very dangerous for your passenger and a potential crime if an accident happens or if you ever sell it with this manipulation - not advised
It is no more dangerous than driving a car without passenger air bag, which I still do occasionally and don't lose any sleep over that. It is annoying more than anything. It is silly design if true that I can't disable useless (for me) child sensor. If I'm not mistaken it is illegal to have child seat on the front seat anyway.
 

·
Registered
Joined
·
473 Posts
Discussion Starter #9
Intuitively, if the SRS controller were going to disable the passenger air bag, then it would illuminate the air bag "off" LED. If the LED is off, then I would expect the air bag to be fully operational.
That's part of the problem here, the Air Bag off LED is still On with adult passenger in.
 

·
Registered
Joined
·
473 Posts
Discussion Starter #11
OK. I didn't realize how easy it is to take this out…

Now, I've never done upholstery work so how do I get the leather off. Is the sensor pad a separate part or integrated into seat cushion?

Also are driver and passenger seats identical? I wouldn't mind swapping them.
 

Attachments

·
Registered
Joined
·
14 Posts
MY 99 sl500, SRS light on , Air bag light off is on. Check all wirings but all good so the problem is sensor. You can try to dectivate by the switch on the side of the passenger seat (didn't help on mine). Can't find the part on line and have no time to go to dealer end up with order emulator from Ireland. all lights is off. I don't have kid and won't put kid in car anyways. For me, If you don't put kid in the front seat, this is the cheaper and easier way than replace the sensor.
 

Attachments

·
Premium Member
Joined
·
4,164 Posts
OK. I didn't realize how easy it is to take this out…

Now, I've never done upholstery work so how do I get the leather off. Is the sensor pad a separate part or integrated into seat cushion?

Also are driver and passenger seats identical? I wouldn't mind swapping them.
no seats are not identical, and the drivers and passenger side don't have the same air bag sensor. IIRC the drivers side may not even have one.

try plugging the yellow plug back in and see if the SRS failure goes away. Had that issue on mine once, plug had somehow come loose.
 

·
Registered
Joined
·
473 Posts
Discussion Starter #14
no seats are not identical, and the drivers and passenger side don't have the same air bag sensor. IIRC the drivers side may not even have one.
I didn't mean identical as far as sensors, Gee I hope they didn't put child sensor on driver side…

I should have said symmetrical… so they would fit on the opposite side. If I were to replace sensor I could fit it on Driver seat and put it on passenger side. Or if I were to use emulator I could just swap them without any additional work.

Just a thought because passenger seat is in better condition.
 

·
Outstanding Contributor
Joined
·
4,109 Posts
Also are driver and passenger seats identical?
Yes, except for later models incorporating the air bag sensor in the passenger side.

...end up with order emulator from Ireland.
That emulator likely consists simply of two or three resistors and a diode. Together they all cost less than $1.

The diagnostic manual essentially explains how to bypass the sensor here: STAR TekInfo (bottom of page). Across two sensor wires you connect a "1N4007" diode in series with a 300-ohm resistor, and in parallel with that you place either a 30K-ohm or smaller resistor to show the controller the seat is occupied, or a 75K-ohm or larger resistor to show it is not.
.
 

·
Premium Member
Joined
·
204 Posts
I might be able to help here, I had the same problem and fixed it easily, it came down to a broken wire. I'll come back with a longer description of the problem
 

·
Premium Member
Joined
·
204 Posts
This is what the sensor looks like. Note I pulled the squab out, then the leather cover off the squab, then the sponge seating off the sensor. I have a spare sensor which I bought and in the end did not need it! Before you do all of that check out the condition of the wire leading from the sensor to the plug under the seat. you can see it here in the pic at the very bottom, a grey wire running away from the seat.

Now, when the seat is in place, this wire runs through the metal frame that holds the seat squab in place. The wire flexs ever so slightly as the seat is used. One of the wires had broken inside the grey insulation at the point where it crosses the hole in the metal frame. I found this out after I pulled the whole seat apart unnecessarily. Easy to check continuity with a meter! Hope this helps. COme back with questions if you need to

rgds
k
 

Attachments

·
Registered
Joined
·
473 Posts
Discussion Starter #18
Something is definitely wrong with the sensor or wiring, doesn't matter really. I like the emulator solution, cheap and easy. This sensor would probably be problematic even if replaced and I don't really need it.

I'd still be curious how to remove leather from the seats, just in case I wanted to replace cushion pads. What's the trick to get it off?
 

Attachments

·
Registered
Joined
·
944 Posts
...I'd still be curious how to remove leather from the seats, just in case I wanted to replace cushion pads. What's the trick to get it off?
I've replaced the skin on the bottom of my SL500, it's kinda difficult to explain, but basically, there is a metal channel all around the perimeter of the bottom of the seat. Skins have fiber strips sown in that tucks in those metal channels. To remove, the seat bottom should be in upside down position as you have in the picture, apply firm and even pressure (knee) to the middle of the metal frame, that relieves the tension of the skin and carefully, start pulling the fiber strip from the channel carefully, starting at the back.

Not sure if this helps, but here is someone's blog (early model, but the principle is the same), you can see the fiber strip and the channel fittings R129 500sl Restoration: Reupholstering the 500SL

Regards,
D
 

·
Registered
Joined
·
473 Posts
Discussion Starter #20
Of course this helps, Thanks. I had no idea where to start with this.

I actually just installed the seats back, I didn't even realize how much better (firmer) passenger seat was until just now that it is on MY side. Little cleaner too.

At some point though I might replace both cushion pads. So it's good to know.
 
1 - 20 of 21 Posts
About this Discussion
20 Replies
8 Participants
Eddieba
Mercedes-Benz Forum
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!
Full Forum Listing
Top