GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The powertrain control module (PCM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The PCM applies a 5 volt reference and a low reference to the sensor. When the pressure is low, the sensors voltage is low. When the pressure is high, the sensors voltage is high. The PCM sends the A/C pressure data to the body control module over the Class 2 serial data circuit. The body control module will not request A/C clutch engagement if the A/C pressure is too high.

Conditions for Running the DTC

The body control module must be powered.

Conditions for Setting the DTC

The A/C refrigerant pressure is greater than 2968 kPa (430 psi) for more than 500 milliseconds.

Action Taken When the DTC Sets

The body control module disables the A/C clutch.

Conditions for Clearing the DTC

    • When the A/C refrigerant pressure drops to less than 1386 kPa (201 psi) the body control module will clear the current DTC and go to a history DTC. If A/C is still requested, the body control module will then enable the A/C clutch.
    • The history DTC will clear after 50 ignition cycles.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

    • If DTC B1324 is stored as a history code it indicates that the body control module did receive a high A/C refrigerant pressure message from the PCM. This code could be caused by an intermittent short to voltage on the A/C refrigerant pressure sensor signal circuit which would cause the PCM to set DTC P0530. The code could also be the result of an actual A/C refrigerant over-pressure condition.
    • It is possible for the refrigerant system pressure to exceed 2968 kPa (430 psi) during extended engine idle speed with A/C ON and ambient temperatures greater than 41°C (105°F). Other possible causes are:
       - An overcharged A/C system
       - A failed A/C refrigerant pressure sensor
       - Blockage in a refrigerant line
       - Debris in front of the A/C condenser
       - Radiator or A/C condenser air shields missing or out of location
       - Inoperative engine cooling fans
       - Extended periods at idle in city traffic followed by rapid acceleration
       - Aftermarket products affecting cooling system performance
    • If the concern is intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Wait one minute for the A/C system pressure to equalize.
  4. With a scan tool, observe the current DTC list in the Body Control Module.

Is DTC B1324 stored as current?

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Go to Step 3

Go to Diagnostic Aids

3

  1. Connect the J 43600 ACR 2000 Air Conditioning Service Center.
  2. Observe the A/C Pressure parameter in the Body Control Module A/C Information data list using the scan tool.

Does the scan tool indicate system pressure near the gauge pressure within the specified range?

+138 to -138 kPa

(+20 to -20 psi)

Go to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Go to Step 4

4

Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

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Go to Step 5

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5

  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?

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Go to Step 2

System OK