Engine-CodesGMC – P077C 2015 GMC Sierra

P077C 2015 GMC Sierra Code - Transmission Output Speed Sensor Circuit Low Voltage

Quick Answer

The P077C diagnostic trouble code (DTC) for a 2015 GMC Sierra indicates a problem with the transmission output speed sensor circuit registering low voltage. Common causes include Faulty output speed sensor, Damaged wiring or connectors in the sensor circuit, Corrosion in the sensor connections. 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
P077C 2015 GMC Sierra indicates Transmission Output Speed Sensor Circuit Low Voltage.
Common causes
Common causes include Faulty output speed sensor, Damaged wiring or connectors in the sensor circuit, Corrosion in the sensor connections.
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 16, 2024
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Code P077C 2015 GMC Sierra Description

The P077C diagnostic trouble code (DTC) for a 2015 GMC Sierra indicates a problem with the transmission output speed sensor circuit registering low voltage. This sensor is responsible for monitoring the speed of the output shaft of the transmission. The information it provides is crucial for the proper functioning of the transmission system, as it helps the vehicle's computer control various aspects such as shift points, torque converter lockup, and overall performance.

OBDII Code P077C 2015 GMC Sierra - Transmission Output Speed Sensor Circuit Low Voltage
P077C 2015 GMC Sierra Code - Transmission Output Speed Sensor Circuit Low Voltage

Common Causes of P077C 2015 GMC Sierra

  1. Faulty output speed sensor
  2. Damaged wiring or connectors in the sensor circuit
  3. Corrosion in the sensor connections
  4. Issues with the vehicle's computer
  5. Low transmission fluid level or contaminated fluid

Symptoms of P077C 2015 GMC Sierra

  1. Erratic shifting behavior
  2. Harsh or delayed shifting
  3. Transmission slipping
  4. Transmission going into limp mode
  5. Illumination of the Check Engine Light

How to Fix P077C 2015 GMC Sierra

  1. Begin by conducting a thorough inspection of the output speed sensor and its wiring harness for any visible damage or corrosion.
  2. Test the output speed sensor using a multimeter to check for proper resistance and voltage output.
  3. Replace the output speed sensor if it is found to be faulty.
  4. Repair or replace any damaged wiring or connectors in the sensor circuit.
  5. Clear the DTC from the vehicle's computer using a scan tool and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P077C 2015 GMC Sierra

The typical repair costs for addressing a transmission output speed sensor circuit low voltage issue can range from $150 to $300, including parts and labor. However, it's important to note that specific diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. It's recommended to check with local shops for a more accurate estimate. Labor rates typically range between $80 and $150 per hour, with rates potentially higher at dealerships or in metropolitan areas, and lower at independent shops.

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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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