ecm test question - tbi

[hjs]

there's a 'set timing' connector on the wiring harness for tbi years (i think) 87 to 95. it's a tan/black wire.
if you unplug the connector you bypass the ecm, but the motor will run, and you can set initial timing.
would this also be a good way to test for a faulty ecm? it the motor runs with the tan/black wire unplugged, but does not run with it plugged, wouldn't this point to a bad ecm?