My experience tells me you do not need to worry about whether analog or digital for grounding the pin. The analog accepts it as a diagnostic program signal. The digital will just see a temporary communications breal down. The phone line will be pulled low so to speak. This line is not hurt by pulling low and probably won't set any codes on any system I know, let alone damage it.

My experience says that Bosch and MB designed systems that were pretty carefull about casual obsrvation. The control units are protected against most circuit problems internally. Even the power command signals are current limited to protect against shorts to ground. Most sensor inputs are protected against both short to B+ and short to ground. The way to hurt one is to shoot high voltage through one.

I am not familiar enough with computers in general to speak to communications protocols. Most diagnostic comminications is done at 10kps (rounded out). The cars buss systems can be running to 500kps. The communications rate might have changed already but is scheduled to go to CAN speed by 2005 I think.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician