Engine-CodesGMC – P0979 2018 GMC Sierra

P0979 2018 GMC Sierra Code - Shift Solenoid Valve 3 Control Circuit Low Voltage

Quick Answer

The P0979 diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates a problem with the Shift Solenoid Valve 3 Control Circuit, specifically reporting low voltage. Common causes include Faulty shift solenoid valve 3, Damaged wiring or connectors in the control circuit, Low transmission fluid levels. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0979 2018 GMC Sierra indicates Shift Solenoid Valve 3 Control Circuit Low Voltage.
Common causes
Common causes include Faulty shift solenoid valve 3, Damaged wiring or connectors in the control circuit, Low transmission fluid levels.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Table of contents Created and updated by William Orellana on Sep 14, 2024
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Code P0979 2018 GMC Sierra Description

The P0979 diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates a problem with the Shift Solenoid Valve 3 Control Circuit, specifically reporting low voltage. This code is typically triggered when the powertrain control module (PCM) detects that the voltage signal from the shift solenoid valve 3 control circuit is below the expected range. The shift solenoid valve 3 is responsible for controlling the hydraulic pressure that engages the third gear in the transmission.

OBDII Code P0979 2018 GMC Sierra - Shift Solenoid Valve 3 Control Circuit Low Voltage
P0979 2018 GMC Sierra Code - Shift Solenoid Valve 3 Control Circuit Low Voltage

Common Causes of P0979 2018 GMC Sierra

  1. Faulty shift solenoid valve 3
  2. Damaged wiring or connectors in the control circuit
  3. Low transmission fluid levels
  4. Malfunctioning PCM

Symptoms of P0979 2018 GMC Sierra

  1. Difficulty shifting gears, especially into third gear
  2. Harsh or delayed shifting
  3. Erratic behavior while driving
  4. Transmission slippage

How to Fix P0979 2018 GMC Sierra

  1. Begin by conducting a thorough inspection of the shift solenoid valve 3, wiring, and connectors for any visible damage or corrosion.
  2. Test the shift solenoid valve 3 using a multimeter to check for proper resistance and continuity.
  3. Check the transmission fluid level and condition, topping off or replacing as needed.
  4. Clear the DTC from the PCM memory using a diagnostic scan tool and test drive the vehicle to ensure the issue has been resolved.
  5. If the problem persists, consider seeking professional help to diagnose and repair any underlying electrical or mechanical issues.

Cost to Fix P0979 2018 GMC Sierra

The cost of repairing a P0979 code on a 2018 GMC Sierra can vary depending on the specific cause of the issue. On average, the parts for a shift solenoid valve replacement can range from $100 to $300, while labor costs can add another $100 to $200. Overall, the total repair cost may fall between $200 and $500. It's important to note that these estimates are general and can fluctuate based on factors such as location, labor rates, and additional repairs needed. It's recommended to consult with a trusted mechanic or dealership for a more accurate cost estimate.

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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.

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