DTC P1540: A/C Pressure Sensor

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing system check, go to next step.
Connect scan tool. Turn ignition on. Wait one minute for A/C system pressure to equalize. Using scan tool, observe A/C PRESSURE parameter in DASH INTEGRATION MODULE A/C INFORMATION data list. If DTC P1540 is stored as a current DTC, go to next step. If DTC P1540 is not stored as a current DTC, A/C system pressure may have exceeded 430 psi (30.2 kg/cm² ) during engine idle speed with ambient temperature greater than 105°F (41°C). Check for an overcharged A/C system, a failed A/C refrigerant pressure sensor, debris in front of condenser, radiator or condenser air shields missing or out of location, or inoperative engine cooling fans.
Park vehicle inside or in shade. Open windows to ventilate interior of vehicle. Allow A/C system to equalize (about 2 minutes). Turn off ignition. Connect test gauges to high and low pressure A/C hoses. Using scan tool, observe A/C PRESSURE parameter in DASH INTEGRATION MODULE A/C INFORMATION data list. If scan tool indicates system pressure is near reading on pressure gauge and between -20 to 20 psi (-1.4 to 1.4 km/cm² ), see A/C SYSTEM PERFORMANCE under SYSTEM TESTS. If scan tool indicates system pressure is not near reading on pressure gauge and/or not between -20 to 20 psi (-1.4 to 1.4 km/cm² ), replace A/C pressure sensor. See A/C PRESSURE SENSOR under REMOVAL & INSTALLATION. Clear DTCs using scan tool. Operate vehicle and if DTC resets, return to step 2 and repeat test.