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King of Smart Gadgetry
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Discussion Starter · #1 ·
My air bag light has been on for a while and when I scan it the scanner told me " B1222 Component driver seatbelt has a short circuit to ground." So I ordered a new seat belt buckle from West Corvina. I installed the buckle and it still would not allow me to clear the code. It told me "condition still exists unable to clear code." So I pulled the passenger seat belt buckle and put it on the driver side and put the new one from West Corvina on the passenger side. Well I still got the same error code. So I am thinking either a wire between the buckle and the SRS module is shorted to ground somewhere or the SRS module itself could be faulty. So I pulled out the driver seat and rolled back the carpet enough to see where the buckle wire feeds down through the carpet and it joins other wires and appears to run towards the front of the car. But my problem is I can't find the SRS module. I want to find it and disconnect it to ohm out the 2 wires going to the buckle to see if there is a short to ground. The only diagram I have been able to uncover is from the 2008 Fortwo tech manual. It shows a drawing of the various modules in the Can Bus. N2/7 is the SRS module. It appears to be under the dash in the middle just ahead of the console. I have been unable to find it. The HVAC system takes up the bulk of the room in the center area under the dash. Max is a 2011 and the tech manual is 2008, so maybe they changed the location over the years? Does anyone have knowledge of where the module is exactly located? DCO


 

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In case you weren't aware of it, finding the fault and correcting it will not turn out the airbag warning light and as long as it is on, your airbags will not work. The only way to clear the fault is a visit to a MB dealer, someone with a Star computer, or buy a scanner such as the i-car soft device i980 that works on Merceedes, Sprint and smart cars. I have one of these devices and can vouch that they do work. I have no interest in promoting these scanners....just want to advise other smart owners of their availability.
 

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King of Smart Gadgetry
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Discussion Starter · #4 ·
Wow they really buried that thing. No wonder I couldn't find it. Thank you so much for the picture. DCO
 

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If the seat belts have pre-tensioners like I think they do have, could be an issue with wiring on the seat belt side......
 

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I've had two driver side and one passenger side pre-tensioners fail. That may be the issue.
I also had a bad connector under the passenger seat.
 

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King of Smart Gadgetry
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Discussion Starter · #7 ·
Thanks guys for the heads up. I never thought about the possibility of it being a pretensioner. The one on drivers side hasn't had a cover on it for quite a while. If it is the pretensioner I'm gonna regret pulling the driver seat and the carpet up! I will report on the situation as soon as I get time to check it. DCO
 

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Does someone sit in the passenger seat often? When I pulled the release once it yanked the passenger belt to lock. I made an appointment with the dealer about 50 miles away and then the day of or before I found it locked, relieved the strain, and light went away....
 

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King of Smart Gadgetry
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Discussion Starter · #9 ·
Hi Jesse. No one is hardly ever in the passenger seat. It's hard to get the wife to ride on the Smart anymore. When we go places we usually take her car. I have noticed when I pull the seat belt out to buckle it I have to do it slowly or it locks. Thanks for the tip. DCO
 

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Discussion Starter · #10 ·
I have my Smart torn to pieces at the moment. I had a axle seal leaking so I had to disassemble enough to replace that. I presume it was due to the axle being more articulated from the Daystar lift? Maybe not I know they just sometimes fail but I would have figured they would last more than 53,000 miles....but I should have known better with burned valves at 36,000.
I have the interior in shambles. Pulled both seats and pulled up the carpet. I have the steering wheel off and the column all apart to replace the faulty clockspring. Also have the button bank, radio trim and all the console stuff underneath the dash out to get to the SRS module. Tracing wires and continuity testing them for connectivity from connector to connector and also to verify none of the buckles or pretensioners are shorted to ground as the B1222 error code suggested.
It seems Mercedes saw fit to sometimes not carry the same color per wire per run. You can trace a light green wire with a violet tracer and when it comes to a connector it may leave the other side a different color.
I have a fairly expensive code scanner at work that will clear the error code and turn off the air bag light but as soon as you start the car it returns. I am pretty good at wiring diagrams and tracing or rooting out wires but this problem has kicked my butt. Toaster is going to send me a wiring diagram for the SRS so hopefully that will help.
I have access to the full blown AllData site at the garage and there is no wiring diagram as such. Only archaic drawings with numbered connectors and numbered modules. I have the 2008 Fortwo Tech manual in PDF that circulated around the forum a few years ago. The listing for modules and their numbers are different from the info on AllData. I was querying AllData for a 2011 Fortwo and the tech manual is 2008, so I guess there must have been changes.
I am assuming the SRS module is working or it wouldn't be sending me an error code to begin with. I did the unthinkable as an experiement. I needed to move the car. I had the steering wheel off, clockspring, horn and shift paddles disconnected. Both seats were out of the car so that meant not all the airbags were accounted for at bootup. I got a list of error codes for my trouble. But they all will clear back out with my scanner except for the B1222 drive buckle is shorted. Both buckles are not wired together as far as I can tell and the pretensioners aren't wired to the buckles. The buckle wires head to the front and the passenger articulation sensor too. The driver pretensioner appears to run towards the rear of the car. The buckles run into the main trunk of wires that run up to the front and it is a mass of wires as big around as your arm. A fox and hound wire tracer is useless in such a large group of wires that are too tight to be separated.
It's astounding how many modules and sensors there are on the Fortwo. There is 3 separate CAN BUS circuits that all run at a different clock speed and 2 "linc" circuits that branch off the Can Bus and run at an even slower speed. Some of the sensors are wired separately to their designated module. It is amazing how high tech that little car was for 2008 model car that was probably designed in 2006 or 2007. A lot of the technology is in our present day new cars now but 10 years ago Smart was groundbreaking in the technology and development department. The Fortwo had great crash test ratings and that was no accident (no pun intended). Mercedes really worked at it to make it a great and safe little car below the surface. But they put the hurt on customers like me that does my own repairs because technical data is virtually non existent. No wonder most independent garage won't touch a Smart Car because they know info you need to repair it just isn't out there to get. You would think that since the 451 has been discontinued for a while now that some info would leak out for us loyal Smart owners. Mercedes wanted us to take them to the dealer whether it was from greed or from a liability standpoint, they closely guard info that could be useful to current Smart car owners.

I will keep you posted on the progress. I hope to have Max back together in time for the Ohio April Rally, but who knows? Might not get those Nerf bars installed or several other projects I have waiting in the garage for him. But I just don't want to drive him without the air bags functioning properly. DCO
 

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If you don’t have the wiring yet I suggest you go to https://www.smarttekinfo.com/SmartTek/ and subscribe for a day. I can help you pull it if you get lost. It is nice in that you can get VIN specific wiring diagrams, vs. something that might not match your option codes. (Of course it does not help my W201, about to throw in the towel on that one).

I hope you tried the pull negative battery cable and reconnect before you disassembled Max!

Are you confident the device you used actually cleared the code? I am just starting to have wiring issues on a ‘92 190E, that’s like what 27 years old. It’s too early. Rereading your last post, hopefully you don’t have to replace the ECU!
 
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