WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect the electrical connector from the A/C low pressure switch.
Fig 1: A/C Low Pressure Switch
Courtesy of GENERAL MOTORS CORP.
Remove the A/C low pressure switch from the accumulator.