HVAC System - Automatic

DTC P1545

Diagnostic Instructions

^ Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. (Initial Inspection and Diagnostic Overview)
^ Review Strategy Based Diagnosis for an overview of the diagnostic approach. (Initial Inspection and Diagnostic Overview)
^ Diagnostic Procedure Instructions provides an overview of each diagnostic category. (Initial Inspection and Diagnostic Overview)

DTC Descriptor

DTC P1545: Air Conditioning (A/C) Clutch Relay Control Circuit

Diagnostic Fault Information

Circuit/System Description

The engine control module/powertrain control module (ECM/PCM) controls the A/C compressor clutch based on an A/C request serial data message from the HVAC control module. The ECM/PCM monitors the A/C refrigerant pressure sensor and if pressure is within a specified range, will engage the A/C compressor by grounding the A/C compressor clutch relay control circuit.

B+ is applied to the A/C relay in the RUN/START position and with the A/C compressor clutch relay control circuit grounded by the ECM/PCM, current flows through the coil side of the A/C relay. With current flowing through the coil side of the relay, a magnetic field is created which pulls the switch side of the relay closed, sending current to the A/C compressor clutch, allowing the A/C compressor to be engaged.

Conditions for Running the DTC

An A/C request is received from the HVAC module.

Conditions for Setting the DTC

A short to voltage, short to ground, or open/high resistance is seen on the A/C compressor clutch relay control circuit.

Action Taken When the DTC Sets

DTC P1545 is a Type C DTC

Conditions for Clearing the DTC

DTC P1545 is a Type C DTC

Reference Information

Schematic Reference

HVAC Schematics (HVAC System - Automatic)

Connector End View Reference

HVAC Connector End Views

Description and Operation

Air Temperature Description and Operation (Air Temperature)

Electrical Information Reference

^ Circuit Testing (Component Tests and General Diagnostics)
^ Connector Repairs (Component Tests and General Diagnostics)
^ Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
^ Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Scan Tool Output Controls

Circuit/System Verification

Engine running, command the A/C Relay On and OFF with a scan tool. The A/C compressor clutch should engage and disengage.

Circuit/System Testing

1. Ignition OFF, disconnect the A/C relay.
2. Ignition ON, verify a test lamp illuminates between the relay coil B+ circuit terminal and ground.
--> If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Connect a test lamp between the relay coil B+ circuit terminal and the A/C compressor clutch relay control circuit terminal.
4. Engine running, command the A/C relay ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.
--> If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the 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.
5. If all circuits test normal, test or replace the A/C relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. (Verification Tests)

Control Module References for ECM/PCM replacement, setup, and programming. (Programming and Relearning)