That's the 1.9L eh. I don't have the manual for the '94, but on the '95 it's showing as a standalone circuit - no connection to the ECT sensor nor anything else - just two wires coming off the camshaft position sensor and feeding directly into the PCM.
Because the voltage output generated by the interaction between the magnet and the sensor is at such a low level, the two wires are encased within a grounded screen (protects from RFI), which grounds at the ignition control module, although I highly doubt the screening would be a relevant factor in this.
I'd suspect a failing sensor, or perhaps sensor misalignment. The signal must be present when the engine and sensor are cold because otherwise the engine wouldn't run, but perhaps the amplitude is too low until it heats up. I'd probably remove the sensor, inspect it and reseat it. If that didn't fix it then I'd probably replace it.
Or, another thought, do you know how that magnet is attached? Any chance that it's loose and not being held firmly until the camshaft has heated up?
I'll upload the wiring diagram and sensor removal/installation section later today.