WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Air Conditioning Diagnostics Chart (Pressure Zone A) (Step 1-8)
Courtesy of GENERAL MOTORS CORP.
Fig 2: Air Conditioning Diagnostics Chart (Pressure Zone A) (Step 9-15)