AutoCodes – GMC – P0647 2018 GMC Sierra

P0647 2018 GMC Sierra Code - Air Conditioning Compressor Clutch Relay Control Circuit High Voltage

Quick Answer

When the Air Conditioning (A/C) switch is pressed, the Heating, Ventilation, and Air Conditioning (HVAC) control module sends an A/C request message to the Engine Control Module (ECM) via serial data. Common causes include Faulty Air Conditioning (A/C) Compressor Clutch Relay, Air Conditioning Compressor Clutch Relay harness is open or shorted, Air Conditioning Compressor Clutch Relay circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: P0647 2018 GMC Sierra indicates Air Conditioning Compressor Clutch Relay Control Circuit High Voltage.
Common causes: Common causes include Faulty Air Conditioning (A/C) Compressor Clutch Relay, Air Conditioning Compressor Clutch Relay harness is open or shorted, Air Conditioning Compressor Clutch Relay circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 188

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 17, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0647 2018 GMC Sierra Description

When the Air Conditioning (A/C) switch is pressed, the Heating, Ventilation, and Air Conditioning (HVAC) control module sends an A/C request message to the Engine Control Module (ECM) via serial data. The ECM then grounds the A/C compressor clutch relay coil control circuit, closing the relay contacts. The closed relay contacts provide voltage to the compressor clutch causing it to engage. The Diagnostic Trouble Code (DTC) will be set when the ECM detects a short to voltage at the A/C compressor clutch relay control circuit.

OBDII Code P0647 2018 GMC Sierra - Air Conditioning Compressor Clutch Relay Control Circuit High Voltage - AutoCodes.com — P0647 2018 GMC Sierra Code - Air Conditioning Compressor Clutch Relay Control Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0647 2018 GMC Sierra?

Faulty Air Conditioning (A/C) Compressor Clutch Relay
Air Conditioning Compressor Clutch Relay harness is open or shorted
Air Conditioning Compressor Clutch Relay circuit poor electrical connection
Faulty Air Conditioning Compressor Clutch
Faulty Engine Control Module (ECM)

How to Fix the DTC P0647 2018 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0647 2018 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0647 2018 GMC Sierra code?

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Need Help with the Code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0647 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code P0647 in a 2018 GMC Sierra related to the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage?

- Common symptoms include the air conditioning system not engaging, intermittent cooling, or a complete failure of the air conditioning to function.

2. What are the possible causes of OBDII code P0647 in a 2018 GMC Sierra?

- The code P0647 in a 2018 GMC Sierra can be triggered by issues such as a faulty air conditioning compressor clutch relay, damaged wiring in the circuit, or a malfunctioning PCM (powertrain control module).

3. How can I diagnose the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage issue in my 2018 GMC Sierra?

- Use a multimeter to test the voltage at the relay and check for any visible signs of damage or corrosion in the wiring connected to the relay. It's also advisable to perform a thorough inspection of the relay itself.

4. Is it safe to continue driving my 2018 GMC Sierra with OBDII code P0647 related to the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage?

- While the vehicle may still be operable, it is not recommended to drive with a malfunctioning air conditioning system, especially in hot weather. Immediate attention and repair are advisable to prevent further damage.

5. Can I reset the OBDII code P0647 in my 2018 GMC Sierra related to the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage without fixing the issue?

- Resetting the code without addressing the underlying problem will likely result in the code reappearing once the system detects the fault again. It's crucial to diagnose and repair the root cause of the issue.

6. What are some repair tips for fixing OBDII code P0647 in a 2018 GMC Sierra associated with the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage?

- Start by checking and potentially replacing the air conditioning compressor clutch relay. Ensure all wiring connections are secure and free of damage. If needed, seek professional assistance for a thorough diagnosis and repair.

7. How can I prevent OBDII code P0647 from reoccurring in my 2018 GMC Sierra after repair?

- Regularly inspect the air conditioning system, including the compressor clutch relay and associated wiring, to ensure everything is functioning correctly. Address any issues promptly to prevent the code from reoccurring.

8. Can extreme weather conditions contribute to triggering OBDII code P0647 in a 2018 GMC Sierra related to the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage?

- Extreme heat or cold can potentially exacerbate existing issues with the air conditioning system, including the relay control circuit. It's essential to maintain the vehicle properly, especially in harsh weather conditions.

9. Should I attempt to repair OBDII code P0647 in my 2018 GMC Sierra myself, or is it best to seek professional help?

- While basic checks like inspecting wiring connections can be done by DIY enthusiasts, diagnosing and repairing electrical issues like the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage problem is best left to trained professionals.

10. Can a faulty PCM (powertrain control module) be the sole reason behind OBDII code P0647 in a 2018 GMC Sierra related to the Air Conditioning Compressor Clutch Relay Control Circuit High Voltage?

- A malfunctioning PCM can indeed cause code P0647, but it is essential to rule out other common causes like a faulty relay or damaged wiring before considering PCM replacement. Consulting a mechanic for a thorough diagnosis is recommended.