P0531

DTC P0531

CIRCUIT DESCRIPTION
The engine control module (ECM) monitors the high side refrigerant pressure via the A/C refrigerant pressure sensor. The ECM applies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure sensor signal to the ECM to vary. When the pressure is high the signal voltage is high. When the pressure is low the signal voltage is low. When pressure is high the ECM commands the cooling fans on. When pressure is too high or too low the ECM will not allow the A/C compressor clutch to engage. When the DTC is set, the ECM does not allow the A/C compressor clutch to engage. This is done to protect the compressor.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC P0531 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit
- DTC P0532 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage
- DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage

CONDITIONS FOR RUNNING THE DTC
- The engine is running.
- The A/C is requested.

CONDITIONS FOR SETTING THE DTC

P0531
The A/C refrigerant pressure sensor signal voltage is less than 0.2 volt or more than 4.88 volts for more than 3 seconds.

P0532
The A/C refrigerant pressure sensor signal voltage is less than 0.2 volt for more than 3 seconds.

P0533
The A/C refrigerant pressure sensor signal voltage is more than 4.88 volts for more than 3 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The ECM stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The ECM disables the A/C compressor clutch.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
- The ECM will report a value of 0 kPa to the HVAC control module.
- The driver information center will display SERVICE A/C SYSTEM.
- The A/C OFF segment will illuminate on the HVAC control module.

CONDITIONS FOR CLEARING THE DTC
- A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- The current DTC will clear when the diagnostic runs and does not fail.
- Use a scan tool in order to clear the diagnostic trouble code.

DIAGNOSTIC AIDS

IMPORTANT: Be sure to verify that the ECM engine grounds are secure and clean.

If DTC P0532 or P0533 cannot be duplicated, reviewing the Failure 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.

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections.

TEST DESCRIPTION

Step 1 - Step 9:

Step 10 - Step 16:

The numbers below refer to the step numbers on the diagnostic table.
3. Tests for the proper operation of the circuit in the low voltage range.
4. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
5. Tests for a short to voltage in the 5-volt reference circuit.