from what I recall, there is no sensor, it's an electirical componet that can just go bad, it has to sense that the PCM and BCM have the same VIN programmed into them, at which point, it will allow the vehicle to start, if the passlock system has difficulty accessing those 2 computers, it will not allow the car to start.
a shot of air wouldn't clean off any sensor, at most it would blow off dust from the electrical contacts of the ignition switch, and allow for a more "direct" contact of the electrical prongs.
You may get away with taking off the ignition switch and using contact cleaner on it to help clean the electrical connections, otherthan that, the switch may just be going bad, or the passlock could as well.