In Reply to: ASC posted by W.Lewis on July 03, 2000 at 18:57:57:
You have the full ASC+T, but not the DSC.
To the best of my knowledge all E39's (from introduction) had the full ASC+T.
It's operation is as follows:
Acceleration is further controlled by the ASC+T ( Stability Control + Traction ) system. This is activated each time the car is started, but can be turned on/off with the ASC key ( lower centre dash ). When off the warning indicator in the instrument cluster is lit.
Normally leave it “ON’. ASC helps prevent loss of forward traction at a drive wheel in conditions of rain, ice, snow, sand, gravel, etc.; by using the wheel sensors to detect if one rear wheel is beginning to slip. In that case it provides the following controls:
- Vehicle speed < 40 kph. - “Traction” program applies brakes, intermittently, to the spinning rear wheel(s). Also reduce engine power if necessary.
- Vehicle speed > 40 kph. - “Stability” program applies brakes “equally” to both rear wheels & adjusts engine power, for stable acceleration or braking.
When it is performing these functions, due to wheel slippage, it flashes the warning indicator in the instrument cluster.
BMW recommends “turning off” the ASC for the following situations:
- when starting off in deep snow, or rocking the car back and forth if stuck in mud or snow.
- to perform a manoeuvre where you need rear wheel slippage ( .i.e. spin the car around on ice ).
Now my esperience is that the system also seems to reduce engine power at slower speeds - but that might be caused by the fact that the "wheel" speed is above 40 (spinning) as opposed to the actual car-road speed.
I am not sure of this issue.
The DSC came later and adds further control - mainly to accomodate lost of control when cornering.
Above speed figures may have been modified since I got this info for 97 model.
This program may also differ depending on whether you have the automatic trans or the manual. Above is for automatic as far as I know. With the automatic there are additinal automated software programs that work with the ASC - helps to choose the right gear in slippery conditions (sometimes referred to as a winter program).
Programs also will prevent an "automatic" downshift when going downhill - also to prevent accidental loss of traction.