Engine-CodesGMC – P077C 2016 GMC Sierra

P077C 2016 GMC Sierra Code - Transmission Output Speed Sensor Circuit Low Voltage

Quick Answer

The P077C diagnostic trouble code (DTC) for a 2016 GMC Sierra indicates a problem with the Transmission Output Speed Sensor Circuit, specifically detecting low voltage. Common causes include Faulty transmission output speed sensor, Wiring issues or loose connections in the sensor circuit, Corrosion or damage to the sensor connector. 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 2016 GMC Sierra indicates Transmission Output Speed Sensor Circuit Low Voltage.
Common causes
Common causes include Faulty transmission output speed sensor, Wiring issues or loose connections in the sensor circuit, Corrosion or damage to the sensor connector.
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 2016 GMC Sierra Description

The P077C diagnostic trouble code (DTC) for a 2016 GMC Sierra indicates a problem with the Transmission Output Speed Sensor Circuit, specifically detecting low voltage. The transmission output speed sensor is a crucial component that monitors the speed of the output shaft of the transmission. This information is essential for the transmission control module (TCM) to determine shift points, torque converter lockup, and other important functions.

OBDII Code P077C 2016 GMC Sierra - Transmission Output Speed Sensor Circuit Low Voltage
P077C 2016 GMC Sierra Code - Transmission Output Speed Sensor Circuit Low Voltage

Common Causes of P077C 2016 GMC Sierra

  1. Faulty transmission output speed sensor
  2. Wiring issues or loose connections in the sensor circuit
  3. Corrosion or damage to the sensor connector
  4. Issues with the TCM
  5. Electrical problems within the transmission control system

Symptoms of P077C 2016 GMC Sierra

  1. Erratic shifting
  2. Harsh engagements
  3. Transmission slipping
  4. Decreased fuel efficiency
  5. Illumination of the Check Engine Light

How to Fix P077C 2016 GMC Sierra

  1. Begin by diagnosing the issue using a scan tool to confirm the P077C code and pinpoint the exact cause.
  2. Inspect the transmission output speed sensor and its wiring for any visible damage, corrosion, or loose connections. Replace or repair as necessary.
  3. Test the sensor's voltage output using a multimeter to ensure it falls within the specified range.
  4. If the sensor and wiring are in good condition, further diagnose the TCM and other related components for potential faults.
  5. Clear the DTC and test drive the vehicle to verify that the issue has been resolved.

Cost to Fix P077C 2016 GMC Sierra

The typical repair costs for addressing a Transmission Output Speed Sensor Circuit Low Voltage issue can range from $150 to $400, including parts and labor. However, it's important to note that actual costs can vary based on factors such as location, vehicle make and model, and the specific repair shop. Diagnostic time and labor rates can also impact the final cost, with rates typically ranging from $80 to $150 per hour. It's recommended to obtain quotes from local auto repair shops for a more accurate 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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