Transistor switching and the SRS light

[Kibokojoe]

Has anyone ever investigated the use of low voltage or milli amperage to reset the A12 SRS module? Seems to me through pin 20 you should be able to transmit a current to reset the NPN transistor. Based on schematics it appears that a NPN transistor is used as a switch to control whether or not the SRS light is on or off.

[632 Regal]

I bought a 40 dollar do-dad from Shogun that resets everything, no clue about your micro voltage theories. ;)

[shogun]

not $40, $85, but it works on E34 and E32, E30, Peake does NOTwork for SRS reset on our cars, only from built year 1995, see Peake homepage.
And, they sell the SRS tool and the other tool separately.
http://www.bimmernut.com/forum/showthread.php?t=39204
Prices include shipping from Japan to Northern America, Oceania, Asia, Europe

SIR3 digital (20 pin round socket) : US $85.00
This device is for resetting BMW models built from 1987 - 2003 with a 20 pins plug interface; WITHOUT can bus. The unit resets the following functions:
Airbag / SRS Light, Service Interval, Oil Change Indication,
Works on the following models:
3-series E30, 3-series E36, 3-series E46, 5-series E34, 5-series E39,
7-series E32, 7-series E38, X5, Z3 E53, Z8,

[whiskychaser]

Not familiar with the diagram but wont the light come on again when you remove the voltage from the transistor?

[Kibokojoe]

You would think but....there has to be a way they are resetting the switch electronically. Would be nice to have a schematic

[Ross]

If you think you have the ability to figure this out so a simple reset can be done by clowns like me who can't manage to remember when the battery needs to be disconnected I'll donate an SRS module for experimentation.

[whiskychaser]

If you think you have the ability to figure this out so a simple reset can be done by clowns like me who can't manage to remember when the battery needs to be disconnected I'll donate an SRS module for experimentation.
That sounds like the US equivalent of a N England expression: 'I'll show my arse on the town hall steps' if you can. Say hi to Arthur for me Ross:D

[Kibokojoe]

If they are charging $50 plus for a gizmo that resets the oil and service lights which is nothing but shorting a lead to ground for so many seconds.... how much harder will it be to figure out how to reset the SRS. I really think it is nothing more than a NPN resistor and they are resetting this resistor with millivolts on the transmission side of the #20 pin. Would be nice to have a SRS module for experimentation

[shogun]

as you want to spoil my business for the $ 85.00 reset tools :)
I give you some help to solve the mystery :D
Gale tried that in 2006 already, he got the pics etc., here the pics, but he apparently did not succeed or did not continue to work on it.
http://www.nmia.com/~dgnrg/diags1.jpg
he mentioned:
Ok. so I copied the pic of the underside of the reset tool & identifed the pin numbers they are using:

We know that the oil & service reset is done by jumping pins 7 & 19 with a wire, for 5 and 10 seconds respectively. They say in their documentation that the SRS reset is done by shorting the memory chip to clear the fault. As accurately as I can tell, the 2 additional pins they have in their reset tool are pins 12 & 16. I checked the schematic & neither 12 nor 16 go to the SRS module. Anyone have a parts car that will power up to practice on? I don't want to risk messing mine up by experimenting with it while it's functioning properly.

[Kibokojoe]

Isn't 7 the ground?

Are you looking at the same Electrical troubleshooting manual?

[shogun]

all 20 pin plugs have the same setup
http://www.autoshoppingcenter.com/servicelights/Bmw.html

[Kibokojoe]

Based on my schematic
Pin 12 is G2 Alternator, A2 Instrument cluster and A7 ABS control unit

Pin 16 is M201 Meter box, A17 Servotronic control unit and fuse 28

[shogun]

what you are now studying is not the diagnosis box, that is X20 or X21 as it is called for the M70 engine, that are the one or 2 (depending on engine type) besides the diagnostic box. And on my M70 engine they have 25 pins in total, not 20 as the diagnosis box.

[Kibokojoe]

My data is coming from a e34 pdf that is a 1989 535i Electrical troubleshooting manual. Based on "Tester command entering 315 will activate the transistorized switch"

http://i273.photobucket.com/albums/jj225/kibokojoe/transistor1.jpg

I figure you could do the same with the SRS circuit

http://i273.photobucket.com/albums/jj225/kibokojoe/transistor2.jpg

Specifically the transistor marked with the red arrow. I am sure that the transistor highlighted is generic but it is a transistor circuit/switch none the less. When the transistor is shorted to ground the SRS lights come on and when the transistor is activated through the "base" the lights will will go out

http://i273.photobucket.com/albums/jj225/kibokojoe/transistor3.jpg


what you are now studying is not the diagnosis box, that is X20 or X21 as it is called for the M70 engine, that are the one or 2 (depending on engine type) besides the diagnostic box. And on my M70 engine they have 25 pins in total, not 20 as the diagnosis box.

[shogun]

I do not know the details, they are made in Germany and I just sell them, as many people are asking for a SRS reset tool which also works on older BMWs from 1987 -...

So I started importing them and many indy shops want them especially or also for private use. In addition it also incorporates besides the SRS reset the oil/inspection and annual inspection sign reset (annual clock sign only where applicable, depending by country version), but it does not read faults, just resets the warning lights when the fault has been repaired.

Peake does not have this, see here a copy from their website:

Airbag (SRS) Scan/Reset Tools for BMWs 1994-2003:
Reads all SRS fault codes, resets SRS Light!
R5/SRS (plugs in under hood)

R5/SRS-16 (plugs in under dash) R5/SRS-U (plugs in under dash and under hood)
R5/SRS Features:
Models available for most BMWs built between 1994 and 2003 Compatibility notes.
Displays all SRS fault codes, tells you what's wrong.
Resets the "SRS" Light.
Very easy to use
Low cost ($129.99)

[Ross]

Any update on this project??

[Kibokojoe]

Nothing so far. It looks like I will need to purchase Shoguns gizmo and try from that end. Can't find any documentation on the module. Frustrating

[whiskychaser]

I'd guess one of the chips on the board has received a signal causing it to 'latch'- ie it wont reset without the proper signal. If you can see the chip numbers on the board you may be able get a pinout and find what they do. That said, I'm a little uncomfortable about you turning a light out if the result is your airbag doesnt work when you need it