A Communications Adapter will not communicate with an ECM unless the Adapter and the ECM has switched power. The switched power also provides voltage to communication ports (typically found as a 9-pin Deutsch HD connector). Check service information for the application you are working with to determine the proper fuse rating required. Unswitched battery negative is also required.Īll ECM power, switched or unswitched, must be fuse protected. Most machine and all engine ECMs require both switched (key switch) and unswitched battery power. All ECMs require power and ground circuits in order to function. Shown is a diagram of the power circuit for an ADEM III ECM.
