Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P0533 A/C Refrigerant Pressure Sensor A Circuit High

Check engine lightUsually off
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The engine module reads the high-side refrigerant pressure sensor (5 V reference, signal rising with pressure) to switch or regulate the compressor, raise the radiator fans at high pressure and pre-control the compressor load at idle. CARB therefore requires A/C components to be monitored where they alter fuel or ignition control or feed other diagnoses (from 2006–2008). P0533 means the signal voltage is too high – GM above 98 % of the 5 V reference in 80 of 100 samples, from a signal shorted to positive or an open sensor ground. Real very high pressure normally leads to a pressure cut-out within range instead. The compressor is locked out. Warning lamp: GM type C without, Saab 9-4X with, Ford depending on vehicle.

Likely causes

Signal line shorted to positive (e.g. 5 V reference)
Sensor ground open
Pressure sensor faulty internally
Extreme overpressure (overcharge, blocked condenser, fan off)

Symptoms

  • Air conditioning not cooling (compressor off)
  • Radiator fan running permanently
  • Check engine light (depending on the maker)

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–250
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ac refrigerant pressure sensorsensor wiringengine control module

Related codes

P0530P0531P0532P0534P0643

References: gsi.ext.gm.com, saabwisonline.com, roushcleantech.com.