Engine-CodesGMC – P0668 2018 GMC Sierra

P0668 2018 GMC Sierra Code - Control Module Temperature Sensor Circuit Low Voltage

Quick Answer

The P0668 diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates a problem with the Control Module Temperature Sensor Circuit, specifically detecting low voltage. Common causes include Faulty temperature sensor, Damaged wiring or connectors in the sensor circuit, Malfunctioning ECM. 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
P0668 2018 GMC Sierra indicates Control Module Temperature Sensor Circuit Low Voltage.
Common causes
Common causes include Faulty temperature sensor, Damaged wiring or connectors in the sensor circuit, Malfunctioning ECM.
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 17, 2024
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Code P0668 2018 GMC Sierra Description

The P0668 diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates a problem with the Control Module Temperature Sensor Circuit, specifically detecting low voltage. In modern vehicles, the Engine Control Module (ECM) monitors various sensors to ensure optimal engine performance and efficiency. The temperature sensor helps the ECM regulate the engine's operating temperature, ensuring it stays within the optimal range for combustion and overall performance.

OBDII Code P0668 2018 GMC Sierra - Control Module Temperature Sensor Circuit Low Voltage
P0668 2018 GMC Sierra Code - Control Module Temperature Sensor Circuit Low Voltage

Common Causes of P0668 2018 GMC Sierra

  1. Faulty temperature sensor.
  2. Damaged wiring or connectors in the sensor circuit.
  3. Malfunctioning ECM.
  4. Corrosion or poor connections in the sensor circuit.
  5. Electrical issues such as a blown fuse or relay.

Symptoms of P0668 2018 GMC Sierra

  1. Check Engine Light illuminated on the dashboard.
  2. Reduced fuel efficiency.
  3. Engine running too hot or too cold.
  4. Rough idling or stalling.
  5. Engine overheating in extreme cases.

How to Fix P0668 2018 GMC Sierra

  1. Use a scan tool to read the code and confirm the issue.
  2. Inspect the temperature sensor, wiring, and connectors for any visible damage or corrosion.
  3. Test the temperature sensor's resistance and voltage to determine if it is functioning correctly.
  4. Replace the temperature sensor if it is faulty, and repair or replace any damaged wiring or connectors.
  5. Clear the DTC and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0668 2018 GMC Sierra

The typical repair costs for addressing a P0668 code on a 2018 GMC Sierra can vary depending on the specific cause of the issue. In general, replacing a temperature sensor and repairing any damaged wiring or connectors can range from $150 to $300 for parts and labor. However, additional diagnostic time and labor rates at auto repair shops can impact the final cost. It's advisable to check with local shops for a more accurate estimate based on your location and vehicle specifics.

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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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