The PCM(Engine Control Module) monitors the A/C Refrigerant Pressure Sensor. The A/C Pressure Sensor is placed in the high pressure line. This signal indicates how much load the A/C compressor is putting on the engine and is one of the factors used by the PCM in order to determine the idle air control position for the idle speed. The signal is a voltage which is proportional to the A/C pressure from 0 to 5V. Low pressure produces a low voltage signal and high pressure a high-voltage signal.
Checking output signals from A/C pressure sensor under detecting condition, if an signal above 4.65V lasts for more than 10 sec., PCM sets P0533.
Item
Detecting Condition
Possible Cause
DTC Strategy
Detects sensor signal short to high voltage
Poor connection
Short in signal circuit
Open in ground circuit
Faulty A/C pressure sensor
Faulty PCM
Enable Conditions
Engine works
Threshold Value
Sensor output voltage > 4.65V
Diagnostic Time
Continuous (More than 10 seconds failure for every 20 seconds test )
MIL ON Condition
DTC only (NO MIL ON)
Fig.1) Normal waveforms of A/C pressure sensor during the time from turning on A/C switch to turning off A/C switch