When measuring O2 sensor signal voltages, the engine must be running and the heated O2 sensor must be at it's normal operating temperature. Just turning on the ignition is not sufficient unless you just want to measure the heater voltage (about 12V between the heater wires). Normally with the engine off but ignition on, the signal voltage from the O2 sensor is very near zero; not 0.45V.
If it's not a mistake, 1.5V on the signal wire coming from the PCM might indicate a problem. With the engine running and O2 sensor hot, the only voltage on the signal wire should be that generated by the O2 sensor. As mentioned above the signal voltage from a good sensor should vary between about 0.2V and 0.7V which would put the average at about 0.45V, but
the engine must be running and the sensor hot for this to occur.
Try measuring the signal voltage under running conditions, and it will take several minutes of running for the sensor to get hot.
EDIT: This web page might be useful to you: