You disconnected two devices and got results. I can tell you that the EHA is the over riding device as the decel switch only participates in the control of the EHA. So..... You must use the test harness and watch the EHA current when the event occurs. You will, based on above, probably see a -60ma decel cutoff function.
If when both are reconnected (and you watching the current) you again have the fault then remove just the decel switch.
There is a test sequence for the decl function on the CD. I don't remember it. but I know what it looks like and the decel switch is part of it.
Bosch Master, ASE Master, L1
33 years MB technician