Location of the asc module on 1997 bmw - 1997 BMW M3

as you've had the OBD scanned i'd go with getting the codes erased, after noting down what they were, and see if problem persists, if does then change whatever the codes indicate

ASC light is part of the ABS system. ASC means slip control system.When this light comes on because it is integrated with the DME or for a better term ECM (control module) It commands trottle reduction. The ASC uses the wheel speed sensor your only fix is get the ABS or (brake inspection) look at The computure engine management thinks you are slipping.

This is a question you should pose to a salvage yard, or better yet to one of those salvage parts finder services on the web. That is a popular part for cars of this vintage, so good luck.
I presume that you have ruled out the wheel sensors and wiring and have determined that the ASC control module has failed?
BTW, the most common cause of an ASC warning light on this vintage BMW (after damaged wheel sensors) is the ASC throttle (aka Secondary Throttle) which is right next to your regular throttle. If its cable is bound, or its electrical connection is damaged, or anything (such as the throttle boot hose clamp) interferes with the action of its throttle plate, it will prevent the ASC from working.

just like a computer...you shut if off and turn it on and everything is ok. It's the ABS/ASC control module btw.

If you have an automatic transmission, you may have two exclamation points in warning lights on the dash. The one in the circle with gear cogs around its perimeter is an error warning light for the computer in the automatic transmission. I have never had that light, but I would first disconnect the battery to try to clear it, and if that failed, I would have to take the car to a good independent shop that specializes in BMWs. Go to Car Talk website for recommendations for a shop.
The exclamation point in a triangle which in turn is in a circle, located between the speedometer and tach, is for the Automatic Stability Control. It should illuminate when you press the ASC button on the console which turns the ASC off. The light warns you when the ASC is turned off.
If there is a problem with the ASC, the most common problems are: 1) Failed switch in the console. 2) Damage or foreign objects in the wheel speed sensors. There are tooth wheels near the front brake rotors and on the rear axle. There are sensors near the toothed wheels that detect wheel speed. The the sensors must be the correct distance from the toothed wheel. If their wires are chaffed, or the toothed wheel is bent or broken, they won't work. 3) Poor connections on the ASC electrical connectors under the hood. Look on the ASC (outboard) throttle body and on the brake controller module. 4) I once put on a new throttle body rubber boot, and I left the screw on the hose clamp positioned at 12 o-clock, up on top of the boot. The ASC throttle arm collided with the hose clamp screw so the throttle motion was restricted. That set an ASC error code and illuminated the light.

Get BMW Scanner 1.4 cable and software for Windows and read the ABS module trouble codes. That will tell you what the ABS thinks is the problem.
https://www.amazon.com/iSaddle-Scanner-Programmer-Diagnostic-Windows/dp/B008RHJTS2/ref=sr_1_3?ie=UTF8&qid=1515358744&sr=8-3&keywords=Bmw+scanner+1.4

It's pretty common for the ABS modules to need rebuilding. They have some tine bonding wires inside thwt break over time from vibrartion and heat. Should cost around $100, check ebay.
https://www.ebay.com/itm/BMW-5-7-Series-Bosch-5-7-DSC-0265950006-ABS-Brake-Module-Repair-Service/232536849310?epid=13007981967&hash=item362446bb9e:g:9NAAAOSwUwFZ8K7O&vxp=mtr

ABS/ASC module is faulty
CLASSIC ABS FAILURE SYMPTOMS:
- Most of the time, the problem is the ABS module or one of the 4 wheel speed sensors (& sometimes the brake pressure sensor)
- In my 2002 BMW E39 DSC, three orange (warning) cluster display lights lit, ABS, Brake, & DSC
- The 3 warning lights reset when the ignition is turned off, only to repeatedly reappear within minutes of normal driving
- The fault is often intermittent leading you to falsely believe you've resolved the problem (proper diagnosis is important)
- Sometimes the fault only appears when the engine is hot; other times only at speeds over 40 mph
- Carsoft may erroneously show a rear speed sensor failure; but just replacing the speed sensor may make no difference.
- All the work is in correct diagnosis of the problem; parts replacement is trivial (from 1 to six bolts in a few minutes)
- Hence, this BMW E39 ABS 3-warning light DIY will concentrate on understanding and diagnosis of the problem

Check to see if your brake pads and rotors are in good condition. Or if you have replaced the pads yourself and have not reset the wheel sensors this would cause the ABS Antilock Brake System light and the ASC Automatic Stability Control light to stay on as the ASC uses the ABS brakes with computer assistance to control the car

if you changed the asc module, the module has to be programmed/coded after replacement. If it was a new part there should be no problem programming the new control unit. I would recommend taking the vehicle to the dealership to allow them to program the control unit.If you have access to the programming don't forget to take the asc module out of "end of belt line mode" and most likely the steering angle sensor will have to be aligned

When your ASC light is on this is to let you know your Automatic Stability Control system is switched off press the ASC button Till light is off /ASC is on this works with your rev limiter and should stabilized your idle. If the problem persists have your throttle control unit checked as thi can trigger the ASC light as well and may also activate the ABS light if not fixed