AutoCodes – Mercedes-Benz – P0721 Mercedes-Benz

P0721 Mercedes-Benz Code - Output Speed Sensor Range/Performance

Quick Answer

The speed sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse signal. Common causes include Faulty Speed Sensor, Speed Sensor harness is open or shorted, 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 Mercedes-Benz indicates Output Speed Sensor Range/Performance.
Common causes: Common causes include Faulty Speed Sensor, Speed Sensor harness is open or shorted, 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 30,505

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 Jun 14, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0721 Mercedes-Benz Description

The speed sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse signal. The pulse signal is sent to the Transmission Control Module (TCM) which converts it into vehicle speed.

OBDII Code P0721 Mercedes-Benz - Output Speed Sensor Range/Performance - AutoCodes.com — P0721 Mercedes-Benz Code - Output Speed Sensor Range/Performance

What does this mean?

What are the Possible Causes of the DTC P0721 Mercedes-Benz?

Faulty Speed Sensor
Speed Sensor harness is open or shorted
Speed Sensor circuit poor electrical connection

How to Fix the DTC P0721 Mercedes-Benz?

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 Mercedes-Benz 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 Mercedes-Benz code?

Need more information on how to fix the P0721 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0721 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area

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 Mercedes-Benz Code

1. What does the OBDII code P0721 mean on a Mercedes-Benz?

P0721 indicates an issue with the output speed sensor, specifically a range or performance problem. The sensor is not providing expected readings to the transmission control module (TCM).

2. What are the common symptoms of a P0721 code on a Mercedes-Benz?

Symptoms may include erratic shifting, transmission slipping, poor acceleration, the speedometer not working, or the Check Engine Light being illuminated.

3. What causes a P0721 code on a Mercedes-Benz?

Common causes include a faulty output speed sensor, damaged wiring or connectors, transmission fluid issues, or a malfunctioning transmission control module (TCM).

4. Can driving with a P0721 code damage my Mercedes-Benz?

Yes, driving with a P0721 code can lead to further transmission issues, reduced fuel efficiency, and potential safety risks due to erratic shifting.

5. How is the P0721 code diagnosed?

A technician will typically use a scan tool to confirm the code, inspect the output speed sensor and its wiring, check for transmission fluid issues, and test the TCM for proper functionality.

6. How do I fix a P0721 code on my Mercedes-Benz?

Repairs may involve replacing the output speed sensor, repairing damaged wiring or connectors, ensuring proper transmission fluid levels, or reprogramming or replacing the TCM if needed.

7. Where is the output speed sensor located on a Mercedes-Benz?

The output speed sensor is typically located on the transmission, near the output shaft. Its exact position can vary by model.

8. How much does it cost to fix a P0721 code on a Mercedes-Benz?

Repair costs vary but generally range from $150 to $400 for sensor replacement. Additional costs may apply for wiring repairs or TCM replacement.

9. Can low transmission fluid cause a P0721 code on a Mercedes-Benz?

Yes, low or dirty transmission fluid can affect sensor readings and cause a P0721 code. Always ensure fluid levels and quality are adequate.

10. Is it safe to clear the P0721 code without fixing the issue?

Clearing the code without addressing the root cause may temporarily turn off the Check Engine Light, but the issue will likely return and could cause further damage.