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      04-06-2011, 01:25 PM   #23
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tape over the airbag light. Hahaha
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      04-06-2011, 02:39 PM   #24
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I should have an update by the end of next week. I had some delays in getting the car into the shop, etc etc. I'm also super eager to see what you can come with!

pokeybritches: No worries at all! I'm just glad we're knocking this problem out once and for all. Attacking it from multiple angles is the way to go so we can give people options!

Roffle Waffle: I lived in Manhattan for too long and saw too many cabbys pull that move to allow myself to do such a thing to the Z. But I hear ya, I almost did it.
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      04-08-2011, 01:27 AM   #25
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Quote:
Originally Posted by Roffle Waffle View Post
tape over the airbag light. Hahaha
My solution will almost be that easy, and will cost less than an airbag reset at the dealer. It won't require you to cut into brand new seats to install the weight sensor, and the airbags will work when you want them to. I will be able to prove the system works, without crashing the car. It's just an idea at this point; I'll be able to pursue it in a couple weeks when I talk to my genius EE buddy.

I don't want to get into it too much, because if there's enough interest I may try and sell them. The problem will be insurance, as I'll be messing with a critical safety feature... something I'll have to look into. I have a feeling the cost will be 25% parts and 75% insurance (if I can even find it ). If I can get it to going I may work up a similar solution for the M3.
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      04-08-2011, 08:57 AM   #26
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Quote:
Originally Posted by pokeybritches View Post
My solution will almost be that easy, and will cost less than an airbag reset at the dealer. It won't require you to cut into brand new seats to install the weight sensor, and the airbags will work when you want them to. I will be able to prove the system works, without crashing the car. It's just an idea at this point; I'll be able to pursue it in a couple weeks when I talk to my genius EE buddy.

I don't want to get into it too much, because if there's enough interest I may try and sell them. The problem will be insurance, as I'll be messing with a critical safety feature... something I'll have to look into. I have a feeling the cost will be 25% parts and 75% insurance (if I can even find it ). If I can get it to going I may work up a similar solution for the M3.
best of luck to you!
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      04-22-2011, 12:01 PM   #27
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Update.

The older sensor mat used in conjunction with the control box puts out a different resistance. Womp. Womp. So, if you want to stay totally OEM, you need to spend the money to get the seat cushion that comes with the sensor mat.

And news on using resistors?
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      04-22-2011, 12:53 PM   #28
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Do you know which exact cable or cables need a resistor. I guess you could do a bunch of trial and error, assuming you can reset the codes each time
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      04-22-2011, 01:40 PM   #29
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I've been working on my 2003 3.0i. I just need the light reset so I can plug it in and see if it works:



I took some measurements and came up with the following:

161k Ohm - resistance with no occupant

8-11k Ohm - resistance with occupant, depending on seating position and weight

I rigged up a circuit with a switch to activate/deactivate the airbag. I'd like to add in a LED but it will require more testing to see if I can overcome the current draw. I used two 100k Ohm resistors in parallel to get a 50k Ohm resistance, in series with another 100k Ohm resistor and finally another 10k Ohm resistor ----> ground (output). Then in parallel I have the switch and a 10k Ohm resistor (should give me 9.4k Ohm of total resistance when closed, well within the occupant threshold). Testing revealed 158k Ohm (within the resistors' tolerances) when the switch was open and 9.4k Ohm when the switch was closed.

I really need a reset tool to finish up testing. If anyone is considering taking out their seats, disconnect the battery after you slide them forward and back to remove the bolts; otherwise, you'll end up with an airbag light. The DIY video I watched simply said keep your key out of the ignition. This is not the case.

With the M I plan on setting the resistance to the level where the "airbag off" light illuminates. I tried using different dumbbells to simulate the weight of a 25, 30, 35, 40, and 50 lb occupant (should deactivate the airbag and illuminate the light on the M) but no luck on the old 3.0i. It has a manual switch on the door, and there's no obnoxious beeping noise when an unbuckled passenger is sensed. Basically, I have no way of proving it works except that the resistance changes and no airbag light illuminates.
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      04-22-2011, 01:47 PM   #30
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Another thing: If anyone knows where I can source the occupancy sensor's plug I'd be very grateful. I'd like to make this truly plug and play. Otherwise, it will require the user to cut off the occupancy sensor's plug and solder on the circuit.

RadioShack sells all kinds of cool things- I had no idea! I was like a kid in a candy store there looking at all the cool LEDs and switches I could install. One looked like the switch they would use to start a nuclear reactor. :Flips switch and says to passenger: "This is your life!" They have "project enclosures" as well so the end result will look like something you would buy in a store rather than a bunch of crap on a breadboard.
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      04-22-2011, 02:47 PM   #31
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good stuff, can't wait to see how you solve it. There's some connectors on Ebay, not sure if they fit
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      04-23-2011, 10:15 PM   #32
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Looks like you're making good progress pokey! Looking forward to your efforts on the M front. I'll check the number on the connector and see if I can do some research on sourcing it so it is truly plug-and-play.

I should say, I'd be most interested in a system that makes it so the passenger airbag(s) deploy. Not sure I understood your post correctly but it seems like you're angling to have the "airbag off" light be illuminated? Wouldn't that mean that the airbag(s) on the passenger side would never deploy? I'm pretty sure this is what the OC3 simulator available from EAS already does. I want to err on the side of caution with airbags and would rather them deploy even if no one is actually in the seat. Now, if it had a switch that'd simulate the seat being either occupied or not occupied, well, that'd be awesome!

So, a word of caution... it's very important to get the resistance right. I know that seems obvious but check out what happened to me...

As I've mentioned, the mat and control box I used on my '06 Z4M was from a pre-'04 Z4 and it didn't work out. The fault that was "resistance too high". Now here's the fascinating part: With the incorrect mat connected, my turn signals and rain sensing wipers and headlight ambient light detection were all VERY wonky. The turn signals would delay coming on or turning off. Turn signal clicks would get skipped or double up. The headlights were at times unresponsive to ambient light (or lack thereof). The rain sensing wipers were also, at times, non-functional. So, given that the mat was the only thing new since the issues started showing, I pulled the plug on the mat and all was well!

In other words, that incorrect resistance (and subsequent fault) was wreaking havoc on other, seemingly unrelated, electrical systems.
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Last edited by JCz04Bimmer; 04-23-2011 at 10:24 PM..
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      04-24-2011, 12:15 PM   #33
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The system I'm rigging up will allow you to turn the airbag on or off with a switch. I wanted to figure out the resistance to achieve the "airbag off" light so that I would know for a fact that the airbag was off when selected off. To know that the airbag is still functioning when selected on, I will be referencing the seat belt warning beep the M makes when a passenger is sensed but unbuckled.

I have some pictures of the (2003 3.0i) plug I can post. I believe the number on it was 293.

It may be a while before I can work up something for the M, since I'm planning to get Recaros/Sparcos for my 3.0i first to see how they work out. The car now has 114k miles of wear, and the stock seats have no lateral support.

If you want to try my method on the M, feel free. Get a multimeter to measure the resistances with and without a passenger, breadboard a circuit with a switch that allows you to select between the two resistances, and solder it all together. Or, if you want to have the airbag on all the time, figure out the resistance with someone sitting in the seat and replace the occupancy sensor with an equivalent resistor. Just be sure to disconnect the battery before you unplug the seat's harness or you WILL end up with an airbag light. If you have any questions or need any help with it, feel free to post here or PM me!
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      04-24-2011, 12:24 PM   #34
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You might still be able to use the other sensor mat, depending on its range of resistances. If the resistance is too high, you can always plug up another resistor in parallel to achieve less resistance. The formula for resistors in parallel is:



The thing you will have to worry about is the range. You may get the resistance right to simulate no passenger, but once a passenger is added it may be way off. If you can give me the measurements of the stock (2004+) sensor mat with/without an occupant I will know what the car is looking for, and I might be able to rig up a circuit for you. I've got the numbers for the 2003 mat already (shown above), so if you can plug up a multimeter to the stock mat, I might be able to make it work.
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      04-24-2011, 02:28 PM   #35
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Does anyone need the electrical schematic from BMW?
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      04-25-2011, 12:00 AM   #36
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Does the car need to see variable resistance ? I would think the easiest way would be to fool the car into thinking you always had a passenger or never had a passenger (if it mean the seat belt chime always was indicated). If there is never a mat showing there is someone sitting in the fixed back seat, are you planning on manually changing the switch to show that you have a passenger in the car ? Seems like a lot of trouble, I can understand the functionality of it due to the airbags, but also am curious how a change in seat style will effect the air bags performance to make that portion of the project a moot point.
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      04-25-2011, 10:57 AM   #37
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Quote:
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Does the car need to see variable resistance ? I would think the easiest way would be to fool the car into thinking you always had a passenger or never had a passenger (if it mean the seat belt chime always was indicated).
Correct. The easiest thing to do would be to fool the car into thinking you always/never have a passenger via a single resistor. However, I want the ability to turn the airbags on or off with the flip of a switch. I don't plan on carrying a car seat but occasionally I do have small cargo in the seat and want the airbag off. ~50% of the time I carry a passenger, and I'll leave the airbag on when they're in the car. But there are times when the airbag would be extraneous or dangerous, so I want the ability to turn it off.

While it sounds complicated, it's really not that hard to create the circuit. Find the resistance with and without a passenger, and make a circuit with those two resistances and a switch. After you do it once it's a matter of duplication. My results will be posted here, and I may consider soldering some up to sell to those that don't want to deal with it... though I'm hesitant because this is a safety feature and don't want to risk being sued because someone forgot to set the airbag accordingly.

I did some more testing yesterday to figure out the voltage change across the sensor ("input voltage") and had some unexpected, though not necessarily bad results. I couldn't get a constant DC voltage from the seat's plug (sensor unplugged). I'm guessing the seat doesn't use a constant 5/9/12V. Instead it's more of a pulse. I had a hard time getting my voltmeter to the plug to take the measurements; the harness had to be plugged in so the seat would have power. It's somewhat difficult to get a multimeter to the back of the seat while it's plugged in. When I finally got a reading, it was jumping all over the place. The range was about .3-.7V with about a 5Hz update rate (guess).

A pulsed input voltage won't affect the operation of the airbag and switch. It does eliminate the ability for me to incorporate a LED, because a LED requires a constant DC voltage. So, it looks like I'll have to have a boring rocker-type switch with no cool light on it.
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      04-25-2011, 11:03 AM   #38
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Quote:
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Does anyone need the electrical schematic from BMW?
Yes that would be extremely helpful for my other projects on down the line! I'm going to experiment with startup settings in the 3.0i (DTC+sport mode on at startup); reducing throttle sensitivity in sport mode; fogs automatically come on with the xenons; DSC control relocated to the steering wheel stalks so the driver can flip it on and off at the track; one-touch top operation...
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      04-25-2011, 04:10 PM   #39
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Getting closer...

Airbag OFF


Airbag ON


I'm waiting on my OBD2 to USB cable so I can reset the airbag light. It should be here sometime early next week. I can also rig it up with an LED that runs off a battery; it will only be illuminated when the airbag is off (to save power). I bought some Velcro backing so I can install the switch anywhere in the cabin.
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      04-25-2011, 04:55 PM   #40
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What software/hardware are you using to reset the SRS AirBag light?
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      04-25-2011, 05:24 PM   #41
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I have an older version of Carsoft that I haven't used before. Supposedly it can reset the light on the older Z4. If that doesn't work out I'll take it to an indy.
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      06-27-2011, 04:09 PM   #42
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Any update on this? So far the only solution that I found was to either get a factory OC3 sensor (donor seat or new $500) and install it or just live with the airbag light and no airbag deployment in case of an accident. EAS does not have a fix for Z4's.

There are no other solutions?
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      06-29-2011, 11:42 PM   #43
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I won't be taking apart the M's seats for at least another 30-40k miles.
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      07-01-2011, 06:51 AM   #44
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Quote:
Originally Posted by idlook2 View Post
Any update on this? So far the only solution that I found was to either get a factory OC3 sensor (donor seat or new $500) and install it or just live with the airbag light and no airbag deployment in case of an accident. EAS does not have a fix for Z4's.

There are no other solutions?
I believe the driver side airbag will fire so long as all the other restraint devices are in place (i.e. belt receptacle). I *think* this is the case because... think about it... the airbag mat is a known failure point for MANY BMW lines and if failure meant ALL airbags were non-functional, you'd hear about that being the case. But, personally, I have not heard that. Of course, the passenger airbag isn't going to fire, though. Not sure about the passenger knee and curtain airbags, though...
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