The Air Conditioning (A/C) system uses an A/C refrigerant pressure sensor mounted in the high pressure side of the A/C refrigerant system to monitor A/C refrigerant pressure. The engine control module (ECM) uses this information to turn ON the engine coolant fans when the A/C refrigerant pressure is high and to keep the compressor disengaged when A/C refrigerant pressure is excessively high or low.

The air conditioning pressure (ACP) sensor operates like other 3-wire sensors. The ECM applies a 5-volt reference and a sensor ground to the sensor. Changes in the A/C refrigerant pressure will cause the ACP sensor input to the ECM to vary. The ECM monitors the ACP sensor signal circuit and can determine when the signal is outside of the possible range of the sensor. When the signal is out of range for a prolonged period of time, the ECM will not allow the A/C compressor clutch to engage. This is done to protect the compressor.

This diagnostic procedure supports the following DTC:

DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage

1. A/C pressure is greater than 4.95 percent of the sensor reading scale.
2. The engine is running.

1. The malfunction indicator lamp (MIL) will not illuminate.
2. The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffers.
3. A history DTC is stored
4. The A/C compressor operation will be disabled while the high voltage indication exists

1. A history DTC will clear after 40 consecutive warm-up cycles without a fault.
2. DTC(s) can be cleared by using the scan tool.
3. Disconnecting the ECM battery feed for more than 10 seconds.

Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection at the ECM.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the A/C pressure display on the scan tool while moving the connectors and wiring harnesses related to the A/C Pressure sensor. A change in the A/C pressure display will indicate the location of the fault.

If DTC P0533 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.