OBD-I cars are not wired for a CKP sensor, because they didn't have one. The OBD-II ECU wants to see a signal and even though you have a harness to plug it into your OBD-I wiring, not all of the right wires are part of the existing wiring. You need to add a wire for it to the harness.

Unfortunately I don't have an OBD-II shop manual so I can't tell you exactly where the CKP sensor is.