P0646 2017 GMC Sierra Code - Air Conditioning Compressor Clutch Relay Control Circuit Low 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
- P0646 2017 GMC Sierra indicates Air Conditioning Compressor Clutch Relay Control Circuit Low 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.
Code P0646 2017 GMC Sierra Description
What are the Possible Causes of the DTC P0646 2017 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 P0646 2017 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 P0646 2017 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.
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Frequently Asked Questions about P0646 2017 GMC Sierra Code
1. What does the OBDII code P0646 mean on a 2017 GMC Sierra?
P0646 indicates a low voltage issue in the Air Conditioning Compressor Clutch Relay Control Circuit, which may prevent the A/C system from functioning properly.
2. What are the common symptoms of code P0646 in a 2017 GMC Sierra?
Symptoms may include the A/C not blowing cold air, the A/C compressor not engaging, or an illuminated Check Engine Light.
3. What causes the P0646 code to appear in a GMC Sierra?
Common causes include a faulty A/C compressor clutch relay, damaged wiring or connectors, a defective A/C compressor clutch, or issues with the powertrain control module (PCM).
4. Can I still drive my 2017 GMC Sierra with a P0646 code?
Yes, the vehicle is typically drivable, but the air conditioning system may not function properly until the issue is resolved.
5. How do I diagnose the P0646 code on a 2017 GMC Sierra?
Start by inspecting the A/C clutch relay, wiring, and connectors for damage or corrosion. Use a multimeter to test for proper voltage and continuity in the circuit.
6. How do I fix the P0646 code on my GMC Sierra?
Repairs may include replacing the A/C clutch relay, repairing or replacing damaged wiring, or, in rare cases, replacing the PCM if it’s faulty.
7. How much does it cost to fix a P0646 code on a 2017 GMC Sierra?
Repair costs can range from $50 to $300, depending on whether you need to replace the relay, repair wiring, or perform more extensive diagnostics.
8. Can a blown fuse cause the P0646 code?
Yes, a blown A/C system fuse can disrupt the circuit and trigger the P0646 code. Check all related fuses as part of your diagnosis.
9. Will clearing the P0646 code with a scan tool fix the problem?
Clearing the code will reset the Check Engine Light temporarily, but the issue will return unless the underlying cause is repaired.
10. Could a failing A/C compressor clutch cause the P0646 code?
Yes, a failing A/C compressor clutch can cause low voltage in the control circuit, resulting in the P0646 code.
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