@nickromano maybe you don't remove the correct resistor. This resistor should be 120 Ohm, 121 written on smd resistor. This resistor is between the CAN-L and CAN-H is simple to understand it. Pin 6 and 14 of OBD connector.

Multiecuscan has big database of ECUs. Which is the method used to implement all protocols to talk with ECU? The datasheet of ECUs is public?

Thank you for the suggestions.