2010 Cadillac CTS Sedan AWD V6-3.0L Page 1558

2010 Cadillac CTS Sedan AWD V6-3.0L Page 1558

瀚慖f not the specified value, replace the relay.

4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test

for less than 2 ohms between terminals 30 and 87.

瀚慖f greater than the specified range, replace the relay.

Repair Instructions

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

* Air Conditioning Compressor Replacement (LF1, LLT) (See: Heating and Air Conditioning/Compressor HVAC/Service and

Repair/Removal and Replacement)Air Conditioning Compressor Replacement (LSA) (See: Heating and Air Conditioning/Compressor

HVAC/Service and Repair/Removal and Replacement)

* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay

Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power

Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))

* Control Module References (See: Testing and Inspection/Programming and Relearning) for HVAC control module and ECM replacement,

setup, and programming

P0647

DTC P0645, P0646, or P0647

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System

Check - Vehicle) prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an

overview of the diagnostic approach.

* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure

Instructions) provides an overview of each diagnostic category.

DTC Descriptors

DTC P0645

- Air Conditioning (A/C) Clutch Relay Control Circuit

DTC P0646

- Air Conditioning (A/C) Clutch Relay Control Circuit Low Voltage

DTC P0647

- Air Conditioning (A/C) Clutch Relay Control Circuit High Voltage

Diagnostic Fault Information

Circuit/System Description

When the A/C switch is pressed, the HVAC control assembly sends a serial data message to the engine control module (ECM) for an A/C request.

This input will request the ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C CLTCH relay. With the relay

contacts closed, battery voltage is supplied to the A/C compressor clutch assembly.

Conditions for Running the DTC

* The ignition voltage is between 9 and 18 volts.

* The engine speed is more than 600 RPM.

* An A/C request is made.