AutoCodes – GMC – P0721 2014 GMC Sierra

P0721 2014 GMC Sierra Code - Transmission Output Speed Sensor Performance

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: P0721 2014 GMC Sierra indicates Transmission Output Speed Sensor Performance.
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 265

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 P0721 2014 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 a noisy output speed signal.

OBDII Code P0721 2014 GMC Sierra - Transmission Output Speed Sensor Performance - AutoCodes.com — P0721 2014 GMC Sierra Code - Transmission Output Speed Sensor Performance

What does this mean?

What are the Possible Causes of the DTC P0721 2014 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 P0721 2014 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 P0721 2014 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.

Need more information about the P0721 2014 GMC Sierra code?

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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 P0721 2014 GMC Sierra Code

1. What are the common symptoms of OBDII code P0721 in a 2014 GMC Sierra?

The common symptoms of code P0721 include erratic speedometer readings, issues with shifting gears, and the transmission going into limp mode.

2. What does the OBDII code P0721 indicate in a 2014 GMC Sierra?

Code P0721 in a 2014 GMC Sierra indicates a performance issue with the transmission output speed sensor.

3. What are the possible causes of OBDII code P0721 in a 2014 GMC Sierra?

Possible causes of code P0721 include a faulty transmission output speed sensor, damaged wiring or connectors, or issues with the transmission control module.

4. How can I diagnose the OBDII code P0721 in my 2014 GMC Sierra?

Diagnosing code P0721 involves checking the transmission output speed sensor for proper operation, inspecting the related wiring and connectors, and testing the transmission control module for faults.

5. Can I continue driving my 2014 GMC Sierra with OBDII code P0721?

It is not recommended to continue driving your GMC Sierra with code P0721 as it can lead to transmission issues and further damage if left unaddressed.

6. How can I repair OBDII code P0721 in my 2014 GMC Sierra?

To repair code P0721, you may need to replace the transmission output speed sensor, repair or replace damaged wiring or connectors, or reprogram the transmission control module.

7. Is it possible to reset OBDII code P0721 in a 2014 GMC Sierra without fixing the underlying issue?

Resetting the code without addressing the underlying issue will only temporarily clear the error code, and the problem will likely reoccur.

8. How much does it typically cost to repair OBDII code P0721 in a 2014 GMC Sierra?

The cost of repairing code P0721 can vary depending on the exact cause of the issue, but it may range from $150 to $500 or more, including parts and labor.

9. Can a DIY enthusiast fix OBDII code P0721 in a 2014 GMC Sierra?

While some DIY enthusiasts may be able to diagnose and replace the transmission output speed sensor, addressing wiring issues or transmission control module problems may require professional expertise.

10. How can I prevent OBDII code P0721 from occurring in my 2014 GMC Sierra?

To prevent code P0721, regularly inspect and maintain your vehicle's transmission system, address any warning signs promptly, and follow the manufacturer's recommended maintenance schedule.