Have you consider the problem could be due to the steering wheel angle sensor?
I have similar problem with the DSC/Brake/Check Engine error with my E46
Try alot of things and manage to resolve it after I recalibrate and initialise the steering wheel angle sensor.
Things I do trying resolve it
1. Change DISA (flap was loose)
2. Clean ICV
3. Clean Throttle body
4. Change brake fluid
5. Flush DSC module using diagnostic function
6. Clean all wheel sensors / change 1 sensor (error detect)
7. Change air hose from filter to throttle body (found some crack after removing it)
BTW, All the aboves did not resolve it.
Found some info about the steering wheel sensor being a possible cause.
Did some further research (google) and 1 solution was to do the calibration of the sensor.
It didnt work the first time but manage the solve it after doing it properly. (4th time)
(The car must be level and steering must be dead straight)
(Recalibration of the steering wheel sensor is done using INPA program)
The DSC alarm will trigger if it detect the steering wheel is not at zero at a certain speed (about 96KPH) based on the
rotation of the 4 wheel sensors. Once the DSCis triggered, the engine will loose "power" and driving become sluggish.
In my case, restarting the car will clear the alarm but it will be trigger after driving again (about 5 minutes)
Funny thing is the alarm never trigger when the car is going above 110KPH. (Look like the car is design to go fast).
Note: I nearly change the DSC module but give up when found out the part are rather expansive even for second hand part.
For e46, the access to the steering wheel angle sensor is quite difficult but I think for E90, it is locate in the steering wheel.
