The air conditioning (A/C) pressure sensor is a transducer that varies resistance according to changes in A/C high side refrigerant pressure. The engine control module (ECM) measures the signal voltage from the A/C pressure sensor, which is a reduced value of the ECM 5-volt reference. The voltage range of the sensor is around 0.2-4.9 volts (0-453 psi) gage pressure. The sensor input is primarily used by the ECM to determine cooling fan speed under A/C operation. The sensor is also used to determine acceptable low/high refrigerant levels for safe A/C operation as well as for A/C idle speed control. DTC P0533 will set if the A/C pressure sensor signal voltage at the ECM is below the calibrated voltage value.

DTC P0533 will set if A/C pressure sensor signal voltage is less than 0.2 volts when:

DTC P0533 diagnostic runs continuously with engine running or cranking.

DTC P0533 is a type D DTC.

To locate an intermittent problem, use the scan tool to monitor AC PRESSURE SENSOR voltage with the ignition ON and the engine OFF. Wiggling the wires while monitoring AC PRESSURE SENSOR voltage may locate the area where an open or short to ground in the wiring may exist.

Important: The scan tool displays A/C HIGH SIDE PRESSURE in absolute pressure like that of a MAP sensor. To convert to gage pressure, subtract 101 kPa (14.7 psi).

Important: Inaccurate readings will occur if resistance measurements are taken on a A/C pressure sensor. The A/C pressure sensor contains an internal amplifier circuit that requires applied voltage to function properly.

Circuit 416 (CMP/EGR/MAF/MAP sensor), circuit 2709 (AC pressure/fuel tank pressure sensor), and circuit 1164 (APP sensor 1) share the same 5-volt reference supply, 5-volt Ref-A.