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.
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 |
The engine is running.
• | 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. |
• | 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. |
• | 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. |
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. |
The numbers below refer to the step numbers on the diagnostic table.
This step tests for the proper operation of the circuit in the low voltage range.
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.
This step tests for a short to voltage in the 5-volt reference circuit.
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 | |||||||
2 |
Important: The ambient air temperature must be above 3°C (38°F).
Does the A/C compressor operate? | -- | Go to Step 3 | |||||||
3 |
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 | ||||||
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 | |||||||
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 | |||||||
Does the voltage measure less than the specified value? | 4.9 V | Go to Step 7 | Go to Step 8 | |||||||
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:
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 |
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 |
Does the DTC reset? | -- | Go to Step 2 | System OK |