Volt

DTC P0531, P0532, or P0533

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.

This is a type D DTC.

This is a type D DTC.

A malfunction within the refrigerant system causing high pressure can cause this DTC to set.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Vehicle in Service Mode, observe the scan tool A/C High Side Pressure Sensor parameter in the ECM data list. The reading should be between 6.8 kPa (1 psi) and 2950 kPa (428 psi).

1. Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B1 A/C refrigerant pressure sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 Ω between the low reference circuit terminal 1 and ground.

⇒	If 10 Ω or greater

2.1.	Vehicle OFF, disconnect the harness connector at the K20 ECM.

2.2.	Test for less than 2 Ω in the low reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K20 ECM.

⇓	If less than 10 Ω

3. Vehicle in Service Mode.
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and ground.

⇒	If less than 4.8 V

4.1.	Vehicle OFF, disconnect the harness connector at the K20 ECM control module.

4.2.	Test for infinite resistance between the 5 V reference circuit and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇓	If infinite resistance

4.3.	Test for less than 2 Ω in the 5 V reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K20 ECM.

⇒	If greater than 5.2 V

4.1.	Vehicle OFF, disconnect the harness connector at the K20 ECM control module, vehicle in Service Mode.

4.2.	Test for less than 1 V between the 5 V reference circuit and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇒	If less than 1 V, replace the K20 ECM.

⇓	If between 4.8-5.2 V

5. Verify the scan tool A/C High Side Presure Sensor parameter is less than 4.8-5.2 V.

⇒	If 4.8-5.2 V or greater

5.1.	Vehicle OFF, disconnect the harness connector at the K20 ECM, vehicle in Service Mode.

5.2.	Test for less than 1 V between the signal circuit terminal 3 and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇒	If less than 1 V, replace the K20 ECM.

⇓	If less than 4.8-5.2 V

6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 2.
7. Verify the scan tool A/C High Side Pressure Sensor parameter is greater than.02 V.

⇒	If.02 V or less

7.1.	Vehicle OFF, disconnect the harness connector at the K20 ECM.

7.2.	Test for infinite resistance between the signal circuit terminal 3 and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇓	If infinite resistance

7.3.	Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K20 ECM.

⇓	If greater than.02 V

8. Test or replace the B1 A/C refrigerant pressure sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.