GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 STS 🢒 DTC 🢒 DTC P0531, P0532, or P0533

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

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for the proper operation of the circuit in the low voltage range.

    2.

  2. 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.

    3.

  3. Tests for a short to voltage in the 5-volt reference circuit.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the A/C High Side Pressure parameter in the Powertrain Engine Data 2 list.

Does the scan tool indicate that the A/C High Side Pressure parameter is within the specified range?

0.2-4.88 V

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the A/C refrigerant pressure sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the A/C High Side Pressure parameter in the Powertrain Engine Data 2 list.

Does the scan tool indicate that the A/C High Side Pressure parameter is less than the specified value?

0.2 V

Go to Step 4

Go to Step 10

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit and the A/C refrigerant pressure sensor signal circuit of the A/C refrigerant pressure sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the A/C High Side Pressure parameter in the Powertrain Engine Data 2 list.

Does the scan tool indicate that the A/C High Side Pressure parameter is greater than the specified value?

4.88 V

Go to Step 5

Go to Step 8

5

  1. Disconnect the fused jumper wire.
  2. Measure the voltage between the 5-volt reference circuit and the low reference circuit of the A/C refrigerant pressure sensor.

Does the voltage measure less than the specified value?

5.5 V

Go to Step 6

Go to Step 7

6

Does the voltage measure near the specified value?

5 V

Go to Step 12

Go to Step 11

7

Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

8

Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for the following:

    • An open
    • A high resistance
    • A short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 9

9

Test the signal circuit of the A/C refrigerant pressure sensor for the following:

    • An open
    • A high resistance
    • A short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10

Test the signal circuit of the A/C refrigerant pressure sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

11

Test the low reference circuit of the A/C refrigerant pressure sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

12

Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

13

Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

14

Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 16

--

15

Replace the ECM. Refer to Control Module References for replacement, setup and programming.

Did you complete the replacement?

--

Go to Step 16

--

16
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK