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Hello All! I have the SRS light on in the dash. The code is 1863-004 (resistance is too high). The following TSB describes how to fix the problem.

Seat Belt Tensioner: All Technical Service Bulletins
SRS - Warning Lamp ON/DTC B1863/B1864 Set

What do you do if the procedure has been performed by a previous owner, and the connections redone by me and the light is still on. One of my scanners (Autel) can turn the light off but it almost immediately comes back on. The iCarsoft scanner claims it cannot communicate with the ECU ... but it can give me the code ...

What is the next step?

As always, any tips, tricks, advice or even replies are welcome!

Chris
 

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I recently had the SRS light on as well. My problem was a bad gas pedal. I was only able to properly diagnose it with the Star Diagnostics System scanner (SDS). Do you have access to SDS? If not, you may want to purchase one. It is very specific to MB.
 

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I on several occasions have had this malfunction show up and each time I simply went under each front seat, disconnected the yellow wire connector (very cramped conditions toward the door side under the seat), spray contact cleaner on each side of the connectors, and reconnect them. I then use my CarSoft i980 to reset the malfunction notice. Each time it seems to work well. Seems that dirt from the floor mats and carpets get into the connectors and interrupt the signal. Your problem may be something more serious, but this simple housecleaning chore seems to work for me. Good luck.
 
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Thanks for the replies!

I recently had the SRS light on as well. My problem was a bad gas pedal.
I'm super curious as to how the gas pedal is connected to the SRS system. Did you have the B1863-004 error? I don't think this is my problem but still I'm curious.

I on several occasions have had this malfunction show up and each time I simply went under each front seat, disconnected the yellow wire connector (very cramped conditions toward the door side under the seat), spray contact cleaner on each side of the connectors, and reconnect them. I then use my CarSoft i980 to reset the malfunction notice. Each time it seems to work well. Seems that dirt from the floor mats and carpets get into the connectors and interrupt the signal. Your problem may be something more serious, but this simple housecleaning chore seems to work for me. Good luck.
Yes, I've done this as well with no luck.

Remember ... This is a car that was involved in a front end crash. Not serious as the air bags did not deploy (see attached).

What would happen if I bypassed the plug completely? should I try installing another repair kit? Should I replace the SRS component attached to the seat belt?

I don't have access to SDS other than going to the stealership. There has got to be a way to diagnose and correct this problem without SDS.

As always, any tips, tricks, advice or even replies are appreciated!

Chris
 

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FWIW you could start throwing parts (and time) at it and quickly be at the cost of a needed tool (SDS). Or buy the tool and have it for the next failure. In the end you will be thousands of dollars ahead of the game with the correct scanner. The SDS is only around $400-$500 or so. Maybe even less if you look around. :smile
 
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FWIW you could start throwing parts (and time) at it and quickly be at the cost of a needed tool (SDS). Or buy the tool and have it for the next failure. In the end you will be thousands of dollars ahead of the game with the correct scanner. The SDS is only around $400-$500 or so. Maybe even less if you look around. :smile
Yeah ... I understand that. The problem is I've heard too many horror stories about getting crap SDS from eBay or Aliexpress. Just kinda leery about the whole thing. I also tried to purchase one via a link that Bobterry99 provided. I tried everything I could think of the purchase it but it kept saying ... please enter required information ... I filled out every space I could find and no luck. I guess I'll just have to keep looking.

UPDATE: I just bit the bullet and got a SDS on the way ...
Thanks for replying!

Chris
 

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I recently had the SRS light on as well. My problem was a bad gas pedal. I was only able to properly diagnose it with the Star Diagnostics System scanner (SDS). Do you have access to SDS? If not, you may want to purchase one. It is very specific to MB.
My mistake. Must have had a brain hiccup. Mine was the ESP light, not SRS.
 

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...and the connections redone by me and the light is still on.
Did you install the connector kit from Mercedes identified in the service bulletin?

When my passenger seat had this problem I substituted electrical connectors from Radio Shack. This was an improvement, but I still had to clear the SRS light every few months. Eventually I installed the repair kit from Mercedes, and the issue disappeared for good.

You could bypass the connectors by soldering the wires together, but you would have to un-solder the wires if ever you were going to remove the seat from the car.
 
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Did you install the connector kit from Mercedes identified in the service bulletin?
I have not done this yet as one of the previous owners has already done it. I'm wondering if replacing the plug again will solve the problem? I'm going to by-pass the plug and do a test today while I'm waiting for the new repair kit to arrive. I'll let y'all know the results

As always, any tips, tricks, advice or even replies are appreciated!

Chris
 
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Well ... I cut the connector switch out and connected the wires directly (with plugs). Pulled out the scanner, read the code and it still is B1863-004. I then hit erase codes, the SRS light goes out and after 1 second, it comes back on. This is leading me to believe this plug/connector is not the problem. I'm thinking it has to do with the sensor that is connected to the seat belt where the yellow connector plugs in. Any thoughts?

My SDS will be here Wednesday, so maybe that can give me more input.

As always, any tips, tricks, advice or even replies are appreciated!

Chris
 

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I finally got a few minutes to hook up my SDS to the car. SDS quick test yielded an interesting find. My Autel scanner can "talk" to the Air Bag Controller and SDS can't. I get the message shown in the picture below. So now, it looks like I need to find the AB controller and replace it. Yay ... Here's a dumb question: Is the AB Controller under the center console on top of the drive shaft tunnel? Like under the ashtray?

Another question: Since this is a crash vehicle, could the impact have been severe enough to kill the AB Controller but not severe enough to deploy the airbags?

But the big question is ... Why can't SDS see/talk to the AB controller and a third party scanner can? Am I doing something wrong? Any ideas are certainly appreciated.

SDS Error Message.jpg


As Always, any tips, tricks, advice and even replies are appreciated.

Chris
 

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'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
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I suppose there is nothing wrong with your SRS/air bag module, Chris, and instead the communication problem is with your multiplexer.

In general, the multiplexer interfaces to the vehicle's various controllers through the CAN's connection to the OBD-II connector. But in the case of the SRS controller there is a dedicated communication line to socket #13 of the OBD-II connector instead of the CAN, and your multiplexer evidently isn't linking to it. I have the notion that this is due to one or more faulty relays which you often hear switching when the multiplexer establishes a connection to a controller.
 

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Thanks for the reply Bob! Now my question is this ... is the problem you describe a SDS problem or a car problem? If anyone could point me in the right direction I sure would appreciate it!

As always, any tips, tricks, advice or even replies are greatly appreciated.

Chirs
 

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So I'm back on the car today. I got the SDS to "talk" to the AB controller. I don't know what I did, but it works. Now I have a message from SDS that states "The airbag control module is already interlocked." Does anyone know if this means the module is broken or the module is ok?

As always, any tips, tricks, advice or even replies are appreciated.

Chris
 

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Chris, I suggest you ask questions that are not answered here over at the W220 part of the forum. Very similar cars and tons of experience over there with SDS. You will probably get a lot more support there. I have a 2005 SL65 and probably spend more time on the W220 side than here.
 
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