Error Code P0533 is defined as A/C Refrigerant Pressure Sensor Circuit High Input. This means the A/C refrigerant pressure sensor is too high to work safely and efficiently, a problem most likely caused by too little or too much refrigerant or defective and inoperable cooling fans.


This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. It is particularly common among Romeo, Chevrolet, Dodge, Ford, Hyundai, Honda, Vauxhall, Volvo, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

The A/C (air conditioning) refrigerant pressure sensor helps the HVAC (Heating, Ventilation, and Air Conditioning) system in regulating the temperature inside the vehicle according to passenger’s settings/demands. This system is connected to two other systems, namely the BCM (Body Control Module) and the ECC (Electronic Climate Control) module, which both monitors the sensors and determines system pressure, which in turn can engage/disengage the compressor accordingly.

The A/C refrigerant pressure sensor works as a pressure transducer, which converts refrigerant system pressure to analog electrical signal, which allows monitoring through the vehicle’s modules. This works by using three wires: a 5-volt reference wire, signal wire, and a ground wire. The modules compare the signal wire’s values to the 5-volt reference, and can instantly calculate system pressures with this info.

Error Code P0533 takes place when the A/C refrigerant pressure sensor is too high. This means the modules has determined an abnormally high electrical value with the A/C refrigerant pressure sensor A or its circuit.

Other related error codes include:

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. The A/C light may flash repeatedly. Other symptoms include:

  • Inaccurate temperature from the fan air
  • Erratic or fluctuating fan air temperature
  • Limited use of HVAC
  • Abnormal operation on the HVAC system
  • A/C compressor is not engaging when needed

Possible Causes

  • A/C system is low or overcharged with refrigerant
  • Inoperable cooling fans
  • Malfunctioning A/C refrigerant pressure sensor
  • Short or open in A/C refrigerant pressure sensor circuit
  • Poor or damaged electrical connections in the refrigerant pressure sensor circuit
  • Blocking, freezing of the expansive valve, or excessive moisture in the system

How to Check

Like many codes, it is best to research this code on the TSB (technical service bulletin) for the specific year, model, and transmission.

To start the diagnosis, you have to check the A/C refrigerant pressure sensor’s operation. Your diagnosis of this code depends on the tools and knowledge you have. Monitor the pressure and other related values while the system is running, and verify the functionality of the sensors using your OBD reader/scan tool.

Note: If you have no prior experience of working with refrigerant, it is highly recommended that you ask the help of a certified professional, as this component can be a safety hazard.

Then, test the A/C refrigerant pressure sensor. This will usually have three wires; test between the pins and record your results. The desired value for this test greatly varies between manufacturers, type of sensor, temperature, etc., so make sure your information is accurate.

Note: When testing pins/connectors, make sure you use the right test pins and multimeter. Damaged pins or connectors could cause future intermittent hard-to-find electrical gremlins.

Lastly, check the wiring. In many cases, these sensors are mounted on an A/C pressure line, or close to the line connection, this is to make sure the harness is routed correctly.

Also in many cases, the sensors can be damaged by moving parts under the hood, which happens when the lines are not secured correctly. Also, make sure the sensor looks good, and its lines are adequately fastened.

How To Fix

  • Technicians will usually use manifold gauges to measure the refrigerant pressure and add or subtract as needed
  • Mechanical issues such as blockages, damaged lines, leaks, and moisture must be fixed
  • The pressure sensor must also be examined, and repair or replaced as necessary
  • Repair or replacement of open, shorted, burnt, and corroded, wires and connectors

Unlike other related error codes, P0533 is not a serious problem, and will not put your life in danger. The worst that could happen is the A/C will not work. However, it can be a complicated fix, which means you may need the services of a qualified technician to help you out. This code will cause you to have a tough time staying cool during hot weather, or using your defogger.