The Candi Module should not plugged into your GM Tech 2 unless you’re working on a later car ..generally 2005 plus. Olders car from 96 should NOT have the Candi Module attached.
OBD I only has 1 ground, so 12 pin adapter connects signal and chassis ground to the Tech 2 cable.
OBD II has chassis and signal ground and they are connected in the cars wiring.
How I was trying to get GM TECH2 CANdi module to work:
Nothing on CANdi end of cable.
Boot screen not showing CANdi present, diagnostics for CANdi says it isn’t seen.
Here I connected OBD I adapter to end of CANdi cable:
OBD I adapter connected.
CANdi module shows up at boot screen.
Green LED flashes about once every second.
Diagnostic screens for CANdi now present. Hit ENTER, 4, 7 to get to this screen.
Self Test Results.
The weird looking screen is because I have not removed the protective plastic yet.