When Monitored and Set Condition:
WARNING: This page is about a different car, the 2004 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
When Monitored: Engine running and the AC Clutch Relay energized.
Set Condition: The A/C pressure sensor signal voltage at the PCM goes below 0.58 of a volt for 2.6 seconds. One Trip Fault.