P0721 Buick 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 Buick 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 Buick 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 Buick?
- 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 Buick?
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 Buick 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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Frequently Asked Questions about P0721 Buick Code
1. What does the OBDII code P0721 mean on a Buick?
P0721 indicates a problem with the Transmission Output Speed Sensor, specifically a performance issue where the sensor’s readings are inconsistent or out of range.
2. What are the common symptoms of code P0721 in a Buick?
Symptoms may include erratic shifting, the transmission stuck in a single gear, the speedometer malfunctioning, reduced fuel efficiency, and the Check Engine Light illuminating.
3. What causes code P0721 to appear in a Buick?
Common causes include a faulty output speed sensor, damaged wiring or connectors, a failing transmission control module (TCM), or internal transmission issues.
4. Can I drive my Buick with the P0721 code active?
It’s not recommended to drive long distances with this code as it can lead to poor performance, transmission damage, or unsafe driving conditions.
5. How do I diagnose the P0721 code on a Buick?
Start by scanning for codes with an OBDII scanner, inspect the output speed sensor and its wiring for damage, and test the sensor’s output voltage with a multimeter.
6. How is the P0721 code typically fixed in a Buick?
Repairs may involve replacing the output speed sensor, repairing damaged wiring, ensuring proper connections, or reprogramming the TCM if necessary.
7. Where is the transmission output speed sensor located on a Buick?
The output speed sensor is typically mounted on the transmission housing near the output shaft.
8. How much does it cost to fix the P0721 code on a Buick?
The cost varies, but replacing the sensor typically ranges from $100 to $300, including parts and labor. Repairing wiring or addressing TCM issues may cost more.
9. Can a bad speed sensor damage the transmission in a Buick?
Yes, if left unresolved, a faulty speed sensor can lead to improper shifting and additional strain on the transmission, potentially causing long-term damage.
10. Do I need to reprogram the TCM after replacing the transmission output speed sensor?
In most cases, reprogramming isn’t necessary, but it depends on your Buick model. Always check the manufacturer’s recommendations.
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