P0533

Circuit Description
The 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 powertrain control module (PCM)/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 (A/C) pressure sensor operates like other 3-wire sensors. The PCM/ECM applies a 5.0 volt reference and a sensor ground to the sensor. Changes in the A/C refrigerant pressure will cause the A/C pressure sensor input to the PCM/ECM to vary. The PCM/ECM monitors the A/C pressure 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 PCM/ECM will not allow the A/C compressor clutch to engage. This is done to protect the compressor.

Conditions for Setting the DTC
- A/C pressure sensor signal is greater than 4.9 volts.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- The A/C compressor operation will be disabled while the low voltage indication exists.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

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

Steps 1 - 9:

Steps 10 - 15:

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. Normal A/C pressure sensor signal voltage is between 0.1 and 4.9 volts. If A/C voltage is within range, review Fail Records data to determine the conditions that were present when DTC P0533 set.
6. The scan tool may not display 5 volts. The important thing is that the PCM/ECM recognizes the voltage as more than 4 volts, indicating that the PCM/ECM and the signal circuit are OK. A test light that illuminates indicates a short to ground in the signal circuit.
7. A short to ground in the 5 volt reference circuit could also set additional DTCs.
11. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.