you are right as is rpm55-they rarely fail. replaced a couple over the years but the 103/104 and 112/113 engines way more often.

i cobbled together a test harness from the abs connectors from a 123, but that vintage, all abs connectors are the same. get the male and female, splice them together with extra terminals to attach scope leads. use lotsa wire to make it easy. plug both ends to the ezl and sender harness and watch the signal. a scope is better because you can see the signal, numbers on a dvom won't help. good luck, chuck.