GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2005 🢒 Isuzu H-Series 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 DTC P1539 or P1546

Diagnostic Instructions

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

DTC Descriptors

DTC P0532: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage

DTC P0533: 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

A/C Compressor Clutch Feedback

P1546

P1546

P1539

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Circuit/System Description

The A/C compressor clutch relay is monitored by the ECM/PCM through the A/C compressor clutch relay feedback circuit.

Conditions for Running the DTC
    • Engine is running.
    • Any of the conditions for setting the DTC are met for 15 seconds.
    • Battery voltage is between 11-18 volts.

Conditions for Setting the DTC

The ECM/PCM detects that the A/C compressor clutch is not on after an A/C request has been made.

Action Taken When the DTC Sets
    • The ECM will not illuminate the malfunction indicator lamp (MIL)
    • The ECM stores the Failure Records.
    • The A/C compressor clutch is disabled.

Conditions for Clearing the DTC
    • The history DTC will clear after 40 consecutive ignition cycles have occurred without a malfunction.
    • The DTC will become history if the ECM no longer detects a failure.

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

HVAC Connector End Views

Description and Operation

    •  Air Temperature Description and Operation
    •  Air Delivery Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Output Controls
    •  Scan Tool Data Definitions

Circuit/System Testing
  1. Ignition OFF, disconnect the A/C compressor clutch relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the relay coil control circuit terminal 85 and ground.
    3. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the relay coil ignition circuit terminal 86 and ground.
    4. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse/breaker is open, test or replace the A/C compressor clutch relay.
  4. Connect a test lamp between the relay coil ignition circuit terminal 86 and the relay coil control circuit terminal 85.
  5. Command the A/C relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    6. ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, ECM/PCM.
    ⇒If the test lamp is always OFF, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM/PCM.
  6. If all circuits test normal, test or replace the A/C compressor clutch relay.

Repair Instructions
    •  Compressor Relay Replacement
    •  Control Module References for ECM replacement, setup, and programming