I will try a pure harness test. If I unplug it at the trans., should I test the inbound pins at the TCU (assuming I can identify them) for resistance? Or will they sow up outbound as ground faults?
FYI: during this process, I did manage to verify that the new Chrysler/Mopar ATF+4 spec trans. fluid is definitely Mercedes Spec. - at about 1/5 the price.