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P0646 2015 GMC Sierra Code - Air Conditioning Compressor Clutch Relay Control Circuit Low Voltage

Quick Answer

The P0646 diagnostic trouble code (DTC) for a 2015 GMC Sierra refers to an issue with the Air Conditioning Compressor Clutch Relay Control Circuit experiencing low voltage. Common causes include Damaged or corroded wiring in the air conditioning compressor clutch relay control circuit, A faulty air conditioning compressor clutch relay, Malfunctioning powertrain control module (PCM). 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
P0646 2015 GMC Sierra indicates Air Conditioning Compressor Clutch Relay Control Circuit Low Voltage.
Common causes
Common causes include Damaged or corroded wiring in the air conditioning compressor clutch relay control circuit, A faulty air conditioning compressor clutch relay, Malfunctioning powertrain control module (PCM).
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 13, 2024
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Code P0646 2015 GMC Sierra Description

The P0646 diagnostic trouble code (DTC) for a 2015 GMC Sierra refers to an issue with the Air Conditioning Compressor Clutch Relay Control Circuit experiencing low voltage. This code indicates that the powertrain control module (PCM) has detected a lower than expected voltage level in the circuit responsible for controlling the air conditioning compressor clutch relay. The air conditioning compressor clutch relay is a crucial component that engages and disengages the air conditioning compressor, allowing the system to function properly.

OBDII Code P0646 2015 GMC Sierra - Air Conditioning Compressor Clutch Relay Control Circuit Low Voltage
P0646 2015 GMC Sierra Code - Air Conditioning Compressor Clutch Relay Control Circuit Low Voltage

Common Causes of P0646 2015 GMC Sierra

  1. Damaged or corroded wiring in the air conditioning compressor clutch relay control circuit.
  2. A faulty air conditioning compressor clutch relay.
  3. Malfunctioning powertrain control module (PCM).
  4. Loose or poor connections in the circuit.
  5. Electrical issues such as a blown fuse related to the circuit.

Symptoms of P0646 2015 GMC Sierra

  1. Ineffective cooling or lack of cooling from the air conditioning system.
  2. Erratic engagement and disengagement of the air conditioning compressor.
  3. Illumination of the check engine light on the dashboard.
  4. Reduced fuel efficiency due to the air conditioning system working harder to cool the interior.

How to Fix P0646 2015 GMC Sierra

  1. Begin by conducting a thorough inspection of the wiring, connectors, and components in the air conditioning compressor clutch relay control circuit to identify any visible damage or issues.
  2. Test the air conditioning compressor clutch relay using a multimeter to determine if it is functioning correctly.
  3. Check the powertrain control module (PCM) for any signs of malfunction and perform diagnostic tests to assess its performance.
  4. Repair or replace any damaged wiring, connectors, or components in the circuit as needed.
  5. Clear the diagnostic trouble codes from the PCM and test the air conditioning system to ensure proper operation.

Cost to Fix P0646 2015 GMC Sierra

The typical repair costs for addressing a P0646 code related to the Air Conditioning Compressor Clutch Relay Control Circuit Low Voltage can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, the cost of parts such as a new air conditioning compressor clutch relay and any necessary wiring or connectors can range from $50 to $200. Labor costs at auto repair shops typically range from $80 to $150 per hour, and the total repair bill can amount to anywhere from $150 to $500 or more, depending on the complexity of the repair process.

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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 P0646 2015 GMC Sierra Code

What does the OBDII code P0646 mean on a 2015 GMC Sierra?

The P0646 code indicates a low voltage issue in the Air Conditioning (A/C) Compressor Clutch Relay Control Circuit, which may affect the A/C system's operation.

What are the common symptoms of the P0646 code in a 2015 GMC Sierra?

Common symptoms include the A/C not blowing cold air, the A/C compressor not engaging, or the Check Engine Light being illuminated.

What causes the P0646 code to appear in a 2015 GMC Sierra?

Possible causes include a faulty A/C compressor clutch relay, damaged wiring or connectors in the circuit, a blown fuse, or a malfunctioning powertrain control module (PCM).

How can I diagnose the P0646 code on my 2015 GMC Sierra?

Start by checking the A/C compressor clutch relay for proper operation, inspecting related wiring and connectors for damage, and testing the voltage at the relay control circuit.

Can I still drive my 2015 GMC Sierra with the P0646 code?

Yes, you can drive the truck, but the A/C system may not function properly, and ignoring the issue could lead to further electrical problems.

How do I fix the P0646 code on a 2015 GMC Sierra?

Repairs may include replacing a faulty A/C compressor clutch relay, repairing or replacing damaged wiring or connectors, or addressing issues with the PCM if necessary.

What tools do I need to troubleshoot the P0646 code?

You will need a digital multimeter, an OBDII scanner, and potentially a wiring diagram for the A/C system to trace the circuit.

Can a blown fuse cause the P0646 code on a 2015 GMC Sierra?

Yes, a blown fuse in the A/C system can result in low voltage in the compressor clutch relay control circuit and trigger this code.

How much does it cost to fix the P0646 code on a 2015 GMC Sierra?

The cost varies depending on the specific issue. Replacing a relay or fuse can cost under $50, while repairing wiring or addressing PCM issues may be more expensive.

Could a weak battery cause the P0646 code on my 2015 GMC Sierra?

Yes, a weak or failing battery can contribute to low voltage issues in electrical circuits, potentially triggering the P0646 code.

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