swwags

I need a little help. My SRS system is showing an error B11a3 (91A3) The resistance value in the ignition circuit containing component R12/2 (Front Passenger Ignition Squib) is too high.
I'm attempting to remove the interior B pillar to access the tensioner. I removed the top section. The bottom section is where I'm having problems. The lower half both front and rear fit under an interior (plastic chrome?) sill plate. It appears that the plate is removed by prying? There are no visible screws and I don't want to break anything obviously.

Can anyone advise on how to remove to gain access to the tensioner?

Answered my own question, they do pry upward. So I was able to remove the tensioner then test the resistance and confirm the error code. OK so now what? Are these wires sending current to the tensioner or from it? From what little I could find, these are feed in, however, I needed my wiring diagrams. Bloody hell. I realized I don't have any for this car. Have them for both my Jaguars but not the s430. I ordered an CD manual, then I can get back to troubleshooting. I can fix a car but can't fix stupid.

I was just going to swap out the belt with a replacement but I'm not much of a fan of swapping parts to fix something. That can get as pricey as a dealership repair in the end. That said, if any MB Mechanics know this is a typical issue and replacement of the tensioner is a common cure, I'd be happy to forgo the troubleshooting

corkshoppe

are you sure its the belt tensioner, try spraying maf cleaner in the belt buckle and see if that gets rid of the light. if it doesnt then does the light go of when you sit in the seat, then its the sensor in the occupation sensor in the seat.

swwags

Actually when the problem started the MB dealership indicated it was a defective seat belt buckle which I replaced. I tried the spray fix but it didn't work.
Since replacing, I purchased AutoEnginuity diagnostic software (also for use on my Jaguar).

When I initially ran the diagnostic, the seat belt code was displayed as well as the code referenced above. I cleared them both, now only the reference to R12/2 remains. The seat belt buckle has not returned.

Thank you for the idea.

fxdeebee

This may help. N2/7 (airbag control module ) is located behind the ashtray in center console

wallyp

While it does appear that you know what you are doing, I do think that we need to add a warning for the less-experienced folks out there that messing with the air bags can easily result in personal injury and totaling the car...

swwags

Thank you fxdeebee for the diagram. It finally warmed up here yesterday and I had at it.
From what I can see in the diagram and in searching forums, there are no additional wire harness connections between R12/2 and the control box. Not sure path the wires run but it appears they run directly from squib to box (no X32 connection between).

As the control units are rarely the issue and Mercedes has a kit to fix the harness, I'd first like to test the connection at the squib.

Visual inspection shows the connector contact pins to be clean. I did receive a replacement ETR seat belt and replaced it and also sprayed with CRC. Same issue, clear code and it instantly re-appears so I don't think the issue is with the unit. So I'd appreciate some advice.

Alternative test approach. Safety pins through the wire on each side of the connector and check resistance. If the resistance is high, could I not just solder the wires directly and bypass the connector altogether to eliminate it as the cause?

This would at least eliminate the need to remove the center console (initially) and disconnect the wires from the unit and check resistance of each wire end to end.

I haven't pulled the ashtray to confirm but assume I can't access the wires just by pulling the ashtray.

Alternative test. Safety pin through the wire on each side of the connector and check resistance, essentially bypassing the connector.

If the doesn't pan out, would soldering a resister in each wire solve the problem? I've read others have done this in a BMW forum but also read on a forum that this doesn't fix the problem and is an amateur fix. Feedback on this please?

The pin kits, and pin removal kits can add up quickly ($$$).


Unencumbered by facts, these are my approach solutions. Feedback appreciated.

FYI, I am fully aware of the risk involved in working with Airbags and do this work with the battery disconnected. And on the bright side, I can dissemble the pillars, remove the ETR, in ten minutes

fxdeebee

n2/7 appears almost easy to get to. Might be able to reach the mounting bolts ( attached a pic ) , hopfully a bit of slack in the harness exists.
As long as you are aware of the possible consequences ...., measuring DC ohms between wiring connector pins at the module ( disconnected ) would tell the first chapter of the story. R12/1 vs R12/2. Note the value for R12/1 as your known good value and if there are no smoking craters then proceed Second chapter would be measuring from connector at module to connector at bad belt ( disconnected ) . Those readings would indicate the health of the copper between module and seatbelt connector. Then the measuring across the pins of the other half of the seatbelt connector.. Using known good reading on R12/1 as a basis for comparison.
I am not a huge fan of pushing pins thru a wire, somehow smacks of voodoo .

swwags

As I mentioned earlier, I did have a defective buckle and replaced it, cleared that error code but the other code, 91A3 remained. "The resistance value in the ignition circuit containing component R12/2 (front passenger ignition squib) is too high.

I did in fact test resistance on either side of the R12/2 connector using safety pins (old timer here using old mechanics trick) and resistance was a bit high. Unplugged, still too high but less so, telling me this was only part of the problem. So even though the contacts looked clean through a magnifying glass, I sprayed the heck out of them with CRC before considering repair. Once dried I did it again, then again.
Since I replaced the buckle, X35/28 was also a suspect. Even though I cleaned the contacts previously when I installed the replacement buckle, I unplugged and cleaned again, then again.

Long story longer, I cleared the code via my AutoEnginuity software, and voila, no more code. Airbags are once again operable.

I found it difficult to believe that a connector (R12/2), so neatly tucked away and out of reach of the elements / virtually unmovable would corrode or loosen, but clearly some corrosion existed. I suspect the connection at X35/28 was the primary culprit.

Thank you many times over fxdeebee for your help!!!

fxdeebee