P0721 2017 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 2017 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.
Code P0721 2017 GMC Sierra Description
The Diagnostic Trouble Code (DTC) will be set when the TCM detects a noisy output speed signal.
What are the Possible Causes of the DTC P0721 2017 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 2017 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 2017 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 2017 GMC Sierra code?
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Frequently Asked Questions about P0721 2017 GMC Sierra Code
What does OBDII code P0721 mean for a 2017 GMC Sierra?
Code P0721 indicates a problem with the Transmission Output Speed Sensor, specifically related to its performance or signal consistency.
What are the common symptoms of code P0721 in a 2017 GMC Sierra?
Symptoms include erratic shifting, the transmission staying in one gear, reduced fuel efficiency, and activation of the check engine light.
What causes code P0721 on a 2017 GMC Sierra?
Common causes include a faulty output speed sensor, damaged wiring or connectors, low transmission fluid levels, or issues with the transmission control module (TCM).
Can driving with code P0721 damage the transmission in a 2017 GMC Sierra?
Yes, prolonged driving with code P0721 can strain the transmission, potentially leading to more severe and costly damage.
How can I diagnose code P0721 on my 2017 GMC Sierra?
Use an OBDII scanner to confirm the code, inspect the output speed sensor and wiring for damage, and check transmission fluid levels.
How do I fix code P0721 on a 2017 GMC Sierra?
Repairs may include replacing the output speed sensor, fixing damaged wiring or connectors, refilling or flushing transmission fluid, or reprogramming the TCM.
How much does it cost to repair code P0721 on a 2017 GMC Sierra?
Repair costs vary but typically range from $150 to $400, depending on whether the sensor, wiring, or other components need replacement.
Can low transmission fluid cause code P0721 on a 2017 GMC Sierra?
Yes, insufficient or contaminated transmission fluid can lead to erratic sensor readings and trigger this code.
Do I need to replace the output speed sensor for code P0721 on a 2017 GMC Sierra?
Not always; inspect the sensor and wiring first. Replacement is only necessary if the sensor is confirmed faulty.
Can a faulty TCM trigger code P0721 on a 2017 GMC Sierra?
Yes, a malfunctioning Transmission Control Module can fail to interpret the speed sensor’s signals properly, leading to this code.
Discuss the causes and fixes for P0721 2017 GMC Sierra OBDII Code
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