OBD 1 and graphing capabilities
I remember that older OBD 1 cars used to just spit out the lamp flash out and numeric codes , that you then had to use a meter to do the pinpoint tests to verify circuits and determine sensor outputs.
Later on car manufacturers engine controllers allowed monitoring live data late 80s. I have a MT 2500 with out back lighting or graphing and forgot whether or not all the later Snap On scanners with back lighting and color graphing allows you to graph data pids of all the later OBD1 cars (that have live data capability) or graphing isn't an option on any OBD1 stuff. I had a Solus , and forgot, don't recall trying to graph scanner data of OBD 1 car.