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For 1990-2009 cars only
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Circuit Description

The engine control module (ECM) monitors the high side refrigerant pressure through an A/C refrigerant pressure sensor. 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. The ECM sends the A/C pressure data to the body control module (BCM) over the GM LAN serial data circuit. This keeps the high side pressure in a normal operating range. This will prevent the A/C compressor clutch from disengaging under normal operating conditions. The BCM will not request A/C compressor clutch engagement if the A/C pressure is too high.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • 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.

Conditions for Setting the DTC
    • A/C pressure of less than 0.3 volts or more than 4.92 volts.
    • The condition must be present for more than 5 seconds.

Action Taken When the DTC Sets
    • The ECM will not illuminate the malfunction indicator lamp (MIL).
    • The ECM will store the conditions present when the DTC set as Fail Records data only.

Conditions for Clearing the DTC
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using the scan tool Clear DTC Information function.

Diagnostic Aids

Test the following conditions:

    • Visually inspect the sensor for contamination or damage.
    • Inspect for the following that may affect the sensors accuracy:
       - A malfunction within the refrigerant system causing low pressure
       - Visually inspect the A/C components and lines for damage.
    • Refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. This step tests for the proper operation of the circuit in the low voltage range.

    2.

  2. This step 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. This step tests for a short to voltage in the 5-volt reference circuit.

    4.

  4. This step tests for a high resistance or an open in the low 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

Important: The ambient air temperature must be above 3°C (38°F).

  1. Turn OFF the ignition.
  2. Inspect the A/C compressor for free rotation operation.
  3. Start the engine.
  4. Place the HVAC control module in the OFF position.

Does the A/C compressor operate?

--

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 3

3
  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 control module (PCM) cooling/HVAC data list.

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

0.1-4.9 V

Go to Diagnostic Aids

Go to Step 4

4

  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 Control Module Engine Data 2 list.

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

0.1 V

Go to Step 5

Go to Step 11

5

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the A/C refrigerant pressure sensor and the 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 Control Module Engine Data 2 list.

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

4.9 V

Go to Step 6

Go to Step 9

6

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

Does the voltage measure less than the specified value?

4.9 V

Go to Step 7

Go to Step 8

7

  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable.
  3. Measure the resistance from the low reference circuit of the A/C refrigerant pressure sensor to a good ground.

Does the resistance measure less than the specified value?

5 ohms

Go to Step 13

Go to Step 12

8

Test the 5-volt reference 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 17

Go to Step 14

9

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

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

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 17

Go to Step 10

10

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

Did you find and correct the condition?

--

Go to Step 17

Go to Step 14

11

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 17

Go to Step 14

12
  1. Disconnect the HVAC control module.
  2. 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 17

Go to Step 14

13

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 17

Go to Step 15

14

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

Did you find and correct the condition?

--

Go to Step 17

Go to Step 16

15

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 17

--

16

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

Did you complete the replacement?

--

Go to Step 17

--

17
  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