For 1990-2009 cars

### Circuit Description

The air conditioning (A/C) refrigerant pressure sensor is used by the engine control module (ECM) to monitor the high side refrigerant pressure. The A/C refrigerant pressure sensor utilizes the following 3 circuits:

• | A 5-volt reference circuit

• | A low reference circuit

• | A signal circuit

The ECM monitors the signal circuit voltage. If the A/C high side pressure is high, the signal voltage is high. If the A/C high side pressure is low, the signal voltage is low. The ECM uses the voltage readings to determine the operation of the A/C compressor and the cooling fans. If the ECM detects an excessively high or low signal voltage, a DTC sets.

### 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.

• | The A/C is requested.

• | DTC P0532 and P0532 run continuously once the above condition is met.

### Conditions for Setting the DTC

#### P0532

• | The ECM detects that the A/C pressure is less than 0.1 volt.

• | The condition exists for more than 10 seconds.

#### P0533

• | The ECM detects that the A/C pressure is more than 4.9 volts.

• | The condition exists for more than 10 seconds.

### Action Taken When the DTC Sets

• | The control module stores the DTC information into memory when the diagnostic runs and fails.

• | The malfunction indicator lamp (MIL) will not illuminate.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• | The driver information center, if equipped, may display a message.

### Conditions for Clearing the DTC

• | A current DTC Last Test Failed clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

• | Clear the DTC with a scan tool.

### Diagnostic Aids

• | For HVAC system concerns, refer to HVAC Preliminary Checks .

• | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

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. Turn ON the ignition, with the engine OFF.
2. Observe the A/C High Side Pressure parameter with a scan tool.

Is the pressure within the specified range?

0.09-4.9 V

Go to Step 3

Go to Step 4

3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn OFF the ignition.
2. Disconnect the A/C refrigerant pressure sensor.
3. Turn ON the ignition, with the engine OFF.
4. Observe the A/C High Side Pressure parameter with a scan tool.

Is the pressure less than the specified value?

0.09 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. Observe the A/C High Side Pressure parameter with a scan tool.

Is the pressure more 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 with a DMM.

Is the voltage more than the specified value?

5.2 V

Go to Step 8

Go to Step 7

7 |

1. Turn OFF the ignition.
2. Measure the resistance between the low reference circuit of the A/C refrigerant pressure sensor and the ECM housing with a DMM.

Is the resistance less than the specified value?

2 ohms

Go to Step 13

Go to Step 12

8 | Important: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.

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 | Important: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.

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

• | 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 17

Go to Step 10

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

• | 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 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 | Test the low reference circuit of the A/C refrigerant pressure sensor for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14
13 | Test for an intermittent and for a poor connection at 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 | Test for an intermittent and for a poor connection at the engine control module (ECM). 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. Did you complete the replacement? | -- | Go to Step 17 | --
17 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate he vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 18

18 | Observe the capture info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK