[DreamCarOwner]

My SRS saga continues. My saga began when my air bag light deployed and the error code was B1222 "driver seatbelt is shorted to ground". Then not too long after that as I was driving home the clockspring had a meltdown. So I ordered a new seat belt buckle from a Smart dealer and when it came I installed it. I ordered a used clockspring from a notable reseller and just installed it.I have an Autel 808 scanner that will access all the devices connected with the SRS system. Replacing the buckle didn't fix the Air bag light. So I disassembled the interior removing seats and carpet and the underdash center cover and also the steering wheel and clockspring. I got a wiring diagram for the SRS from a fellow SCOA member and began tracing wires and testing for resistance and shorts to ground. In the end I didn't find anything notable.
I plugged the SRS module back in and reinstalled the seats and pretensioner. Then I installed the clockspring and steering wheel and driver air bag in the center of the steering wheel. The SRS module is working because I still have an airbag light but not sure if it is working correctly.
The other 2 error codes are B1023 "stage 2 driver airbag has high impedance" and B1003 "stage 1 driver airbag has high impedance". So I am going to remove the steering wheel again and ohm test the replacement clockspring. Since the driver airbag connection to the SRS module runs through the clockspring I am going to assume the clockspring could be bad. I can clear the seatbelt error and the air bag errors. But as soon as the car restarts they reappear. So that tells me I haven't fixed the problem.
I have been researching all over our forum and Smartz and Evilution along with any other resource I can find through a Google or Bing search. There is so much misinformation out there that I do not know what or who to believe. A hard error code is etched into the SRS in the event of an air bag deploying or a crash sensor firing off and then the air bag light goes out because the module shuts itself down and will not operate until it is reset either by a module resetting service or the dealer. I would just replace my SRS module to see if it is faulty but....some say it is tied to your VIN # and therefore another unit wouldn't function out of it's host original car. Some say it isn't tied to a Vin because reputable resellers sell them for replacement all the time and they couldn't do that if they were tied through the VIN.

Since there is no reliable information out there to buy it really puts an independent mechanic like me at a disadvantage. Full blown AllData which I have access to has very limited information on the Fortwo. I am at a loss to troubleshoot the problem. I don't want to drive it without the SRS working because in the event of an accident your only chance of survivng a serious accident is the air bags and pretensioners, so there is alot at stake. So I sit here not knowing what to do next. I have more questions than answers. I feel like I'm trying to solve the DaVinci code. DCO

 

[jzchen]

A Google search came up with side airbag something. Might be chasing the wrong part....

 

[toaster]

Check your codes against Evilution's list at:
https://www.evilution.co.uk/info/obdii_error_codes.htm

Since you have a tool to reset SRS error codes, you could try unplugging some items to see what code they trigger or perhaps it will change from a "short to ground" error to an "open" error.

The guys at SOS Diagnostics may be able to tell you if the SRS module is tied to the vehicle's VIN. If so, they would be the place to reprogram one for your VIN.
S.O.S. Diagnostics

~toaster

 

[jzchen]

Is your Autel unit updated? Try that first...

Maybe it’s a good idea one person in each state invest in a Star Machine, that everyone in that state can chip in and use...

I was looking at a Launch Tech USA X-431 Torque, but now I’m losing confidence in anything but the Star. I’m pretty much giving up on all Mercedes products in the household. Last one with sticker and insurance is a ‘92 190E, OBD-1...

 

[DreamCarOwner]

I thought I would update my SRS situation and what I have done in my limited amount of time I have had lately to work on it. The clockspring I had bought from a reseller turned out to be bad so hence the driver air bag low and high impendance codes I was getting. Replacing the clockspring with a second replacement one again fixed that problem. So then I had 2 codes one of which was new at this point. I had the usual B1222 Component driver seatbelt buckle has a short to ground. On the live data from the scanner it lists the buckle as "connected" but "has a problem". It remains the same whether it is buckled, unbuckled or the wire connector to it is disconnected.

The new error message I then got was B2F00 Control unit N2/7 (restraint systems control unit) is defective. Now if I am right in my idea, the main module of the Smart Can Bus system is the instrument panel cluster. It communicates with the SAM which I thought was the master so to speak, but the instrument panel seems to tie everything together.

Now the instrument panel module was telling me the Air bag module was faulty. The air bag light was still on and I still got the seat belt buckle error so I guess the instrument panel cluster stores the error message from the other modules because otherwise with a dead air bag module I should not have had a air bag light or any error from the seat belt buckle. I should have only had the B2F00 control unit faulty.

So at this point I knew I needed to replace the air bag module. It seems that at several times over the years of producing the 451 every so often they updated the air bag module. So if you do not match the numbers on the module I am assuming it will not work correctly with your Smart due to software version mismatches. My module number was A4519015200/Q03. I found several other series of modules with different number from other series such as: A4519010901 and 4518202785 etc,... The 3 end numbers after the forward slash doesn't seem to matter. The module I purchased had the number 4519015200/Q08 and was the closest number to mine. It's a shame it wasn't the cheapest one available to me.

I installed the module and pulled codes. I still had the B1222 seat belt switch faulty. The B2F00 Restraint system module is faulty was gone so I knew the replacement module was working. But I now had a new error code: B11E1 Fault or disturbance in CAN message from control unit instrument cluster (VIN). So I solved that mystery. THE AIR BAG MODULE HAS A PARTIAL VIN NUMBER FROM YOUR VEHICLE INSIDE IT. If you replace the module you must get the cars VIN number implanted in your new module to clear that code and turn off the airbag light.


Now I saw several ads on Ebay from people that will reset your air bag module. If you are in an accident and an air bag deploys you now have a hard code in your air bag module. The module will not function again until that hard code is cleared from your unit. That's what getting your module reset consists of, a reset from an accident. They cannot rewrite your VIN number on your new module. The following paragraph is a copy of the reply I received from one such reset service on ebay:

Good Afternoon,

Please compare the part numbers of your original part to this replacement airbag control module.
If the part numbers do no match, it is unlikely that the airbag module will work in the vehicle. Also, after installation a new or used replacement airbag control modules will need to be additionally programmed to the VIN of your vehicle (a service that can be provided by someone with a scanner with this capability). Unfortunately, that is not something we do here.

So I am assuming only a Mercedes Star computer can remedy this problem. My Autel MK808 cannot do this even though I can query everything connected to the module in live data mode. All 8 airbags by individual name, motion sensors front and back, yaw sensor(acceleration/ deacceleration),steering angle sensor, seat belt buckles, placement sensor on the passenger seat and weight distribution sensor on the passenger seat that turns off the airbag when the seat is unoccupied or has a child safety seat in it. The module adjusts air bag deployment according to the passenger.

I received some wiring diagrams from OP's on SCOA and I thank you for them. But at this point I needed something more complete to help me figure out what was still going on. So I found a website:

eManualOnline - Car Workshop Manuals, Service Manuals, Repair Manuals, Online Manuals

This site carries multiple manuals for everything known to mankind and I think they are in the UK, and they accept paypal for payment too. They have the Smart Mercedes Benz WIS and ASRA manual that covers Mercedes, Sprinter and Smart. In particular to the Smart it covers 450,451 and Forfour(no use to us). Downloading it and setting it up took a little while. Downloading the file was 17 GB. It took about half an hour to download. Then there are instructions they email to you for another file that setups up your computer for the program. The program runs on a virtual machine which means it sets up up another computer inside of your computer. It takes a lot of space. I set up a 50GB partition for it. It gives you an icon you click into and it brings up a version of windows 7 ultimate with it's own desktop. Then you click into the Mercedes program and everytime it needs to go to the internet for communication with a master server it goes to a file on your local computer called localhost. The program has tons of info and options and as far as Smart is concerned it makes AllData look like childs play.

So I was able to print off wiring diagrams and anything else I needed. But still haven't cracked the problem yet. I reached out to Kane on the Evilution site.

https://www.evilution.co.uk/

Evilution is the holy grail when it comes to Smart information. Kane thinks that maybe my scanner is sending me bogus codes and the problem is not what the scanner is telling me. So I sent him my VIN and we will see if he can add some insight to my problem. If he can't probably nobody can. Evilution is less than $15 per year and totally worth every penny. If you're new to SCOA and haven't looked at his site please do. As far as E manual online I have no affiliation with them but with info so hard to get from Mercedes it is a viable option if you are able to apply the info to fix your little Fortwo.

Lastly here is a picture of what's inside a SRS air bag control module. It's a picture of something that will save your life in the event of an accident. I am guessing that all the onboard capacitors are there in the event of impact happening and the battery being disconnected, the capacitors I assume will store enough power to fire the airbags on impact. I will keep updating until I have solved the problem. DCO

 

[jzchen]

Need a Star Machine to perform “initial startup”.

http://www.mercedesmedic.com/mercedes-benz-srs-airbag-light/