For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0531 00: Air Conditioning (A/C) Refrigerant Pressure Sensor Performance
DTC P0532 00: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage
DTC P0533 00: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5 V Reference | P0532 00 | P0532 00 | -- | --
Refrigerant Pressure Sensor Signal | P0532 00 | P0532 00 | P0533 00 | P0531 00
Low Reference | -- | P0532 00 | -- | --

### Circuit/System Description

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The ECM supplies a 5 V reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the 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 activation of the A/C compressor.

### Conditions for Running the DTC

Engine is running.

### Conditions for Setting the DTC

#### P0531 00

The ECM has received an invalid sensor signal.

#### P0532 00

The ECM detects a short to ground or open at the A/C pressure sensor signal circuit.

#### P0533 00

The ECM detects a short to voltage at the A/C pressure sensor signal circuit.

### Action Taken When the DTC Sets

• | The A/C compressor is disabled.

• | The ECM will illuminate the malfunction indicator lamp (MIL).

### Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Automatic HVAC Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B1 A/C Refrigerant Pressure Sensor.
2. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and ground.

⇒ | If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

3. Test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and the low reference circuit terminal 1

⇒ | If less than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.3 V.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Install a 3 A fused jumper wire between the following signal circuit terminal 3 and the 5 V reference circuit terminal 2. Verify the scan tool A/C High Side Pressure Sensor parameter is greater than 4.8 V.

⇒ | If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. If all circuits test normal, replace the B1 A/C Refrigerant Pressure Sensor

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement

• | Control Module References for engine control module (ECM) replacement, setup, and programming