Circuit/System Verification
WARNING: This page is about a different car, the 2007 Suzuki XL7. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, observe the scan tool A/C High Side Pressure parameter in the ECM. The reading should be between 0.1 and 4.90 volts (1 and 425 psi), and change with pressure.