AutoCodes – GMC – P077D 2015 GMC Sierra

P077D 2015 GMC Sierra Code - Transmission Output Speed Sensor Circuit High Voltage

Quick Answer

The Output Speed Sensor (OSS) is a hall-effect type sensor. Common causes include Faulty Transmission Output Speed Sensor (OSS), Transmission Output Speed Sensor harness is open or shorted, Transmission Output Speed Sensor circuit poor electrical connection. 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: P077D 2015 GMC Sierra indicates Transmission Output Speed Sensor Circuit High Voltage.
Common causes: Common causes include Faulty Transmission Output Speed Sensor (OSS), Transmission Output Speed Sensor harness is open or shorted, Transmission Output Speed Sensor circuit poor electrical connection.
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.

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Code Popularity 478

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 29, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P077D 2015 GMC Sierra Description

The Output Speed Sensor (OSS) is a hall-effect type sensor. The OSS mounts to the automatic transmission case assembly and connects to the control solenoid valve assembly through a 2-wire harness and connector. The sensor faces the park gear teeth. The sensor receives battery voltage on the OSS supply voltage circuit from the Transmission Control Module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the park gear teeth. This signal is transmitted through the OSS signal circuit to the TCM. The TCM uses the OSS signal to determine line pressure, transmission shift patterns, vehicle speed, and gear ratio.
The Diagnostic Trouble Code (DTC) will be set when the TCM detects the vehicle speed sensor signal circuit voltage is 4.75 V or greater for 0.8 s.

OBDII Code P077D 2015 GMC Sierra - Transmission Output Speed Sensor Circuit High Voltage - AutoCodes.com — P077D 2015 GMC Sierra Code - Transmission Output Speed Sensor Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P077D 2015 GMC Sierra?

Faulty Transmission Output Speed Sensor (OSS)
Transmission Output Speed Sensor harness is open or shorted
Transmission Output Speed Sensor circuit poor electrical connection
Faulty Transmission Control Module (TCM)

How to Fix the DTC P077D 2015 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 P077D 2015 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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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.

Frequently Asked Questions about P077D 2015 GMC Sierra Code

1. What does the OBDII code P077D mean for a 2015 GMC Sierra?

P077D indicates that the transmission output speed sensor circuit is registering a high voltage signal, which may affect the transmission's ability to function properly.

2. What are the common symptoms of code P077D in a 2015 GMC Sierra?

Symptoms may include erratic shifting, the transmission stuck in one gear, reduced fuel efficiency, or the check engine light being illuminated.

3. What causes the P077D code to appear in a 2015 GMC Sierra?

Common causes include a faulty output speed sensor, damaged wiring or connectors in the circuit, transmission fluid contamination, or an internal transmission issue.

4. How can I diagnose the P077D code on my 2015 GMC Sierra?

Start by checking the output speed sensor and its wiring for visible damage, testing the sensor with a multimeter, and scanning the transmission control module (TCM) for additional codes.

5. Can I drive my 2015 GMC Sierra with the P077D code active?

Driving with this code is not recommended, as it can lead to further transmission damage or unsafe driving conditions due to erratic shifting.

6. How do I fix the P077D code on my 2015 GMC Sierra?

Repairs may include replacing the output speed sensor, repairing damaged wiring or connectors, or flushing and replacing contaminated transmission fluid.

7. How much does it cost to fix the P077D code on a 2015 GMC Sierra?

The cost varies depending on the exact issue, but replacing the output speed sensor typically costs between $100 and $300, including parts and labor.

8. Can low transmission fluid cause the P077D code in a 2015 GMC Sierra?

Low or contaminated transmission fluid can contribute to the issue by affecting sensor readings or transmission performance.

9. Is the P077D code related to other transmission codes on a 2015 GMC Sierra?

Yes, it may appear with other transmission codes, indicating a broader problem with the transmission system or control module.

10. Do I need to reprogram the TCM after fixing the P077D code on my 2015 GMC Sierra?

In most cases, reprogramming the TCM is not necessary, but clearing the code and performing a test drive is recommended to ensure the issue is resolved.