MB suggests that when running cars on a dyno that the ASR be deactivated by unplugging the ABS/ASR actuator. After testing, the cars controllers will have to be reset to get rid of all the codes which will be set.
They do not want the control unit disconnected as that would interfere with the engine management systems ability to get needed info from the ABS/ASR controller.
Bosch Master, ASE Master, L1
33 years MB technician