AutoCodes – Mazda – P0721 Mazda

P0721 Mazda Code - Erratic Output Shaft Speed

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 Mazda indicates Erratic Output Shaft Speed.
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 5,501

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 Mazda 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 Mazda - Erratic Output Shaft Speed - AutoCodes.com — P0721 Mazda Code - Erratic Output Shaft Speed

What does this mean?

What are the Possible Causes of the DTC P0721 Mazda?

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

How to Fix the DTC P0721 Mazda?

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 Mazda 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 P0721 Mazda Code

1. What are common symptoms of OBDII code P0721 in a Mazda related to erratic output shaft speed?

- Common symptoms include erratic or incorrect vehicle speed readings, harsh shifting, transmission slipping, and illumination of the Check Engine Light.

2. What are the typical causes of OBDII code P0721 in a Mazda?

- The most common causes of P0721 in a Mazda are a faulty output shaft speed sensor, damaged wiring or connectors in the sensor circuit, or issues with the transmission control module.

3. How can I diagnose the OBDII code P0721 in my Mazda if I suspect an issue with the output shaft speed sensor?

- To diagnose P0721 related to the output shaft speed sensor, you can use a multimeter to test the sensor's resistance, check the wiring for continuity and shorts, and inspect the sensor for physical damage or contamination.

4. What are some repair tips for resolving OBDII code P0721 in a Mazda caused by a faulty output shaft speed sensor?

- Repair tips include replacing the output shaft speed sensor with a genuine Mazda part, ensuring proper sensor alignment during installation, and clearing the trouble codes with an OBDII scanner after the repair.

5. Can a malfunctioning output shaft speed sensor cause further damage to the transmission in a Mazda with OBDII code P0721?

- Yes, a malfunctioning output shaft speed sensor can lead to incorrect gear selection, increased transmission wear, and potential transmission overheating if not addressed promptly.

6. Is it safe to continue driving my Mazda with OBDII code P0721 if the symptoms are not severe?

- It is not recommended to drive the vehicle with OBDII code P0721 for an extended period, as unresolved issues related to erratic output shaft speed can lead to transmission damage and safety hazards on the road.

7. How much does it typically cost to repair OBDII code P0721 in a Mazda at a dealership or a local mechanic?

- The cost of repairing OBDII code P0721 in a Mazda can vary depending on the exact cause, but on average, it may range from $150 to $400 for parts and labor.

8. Can resetting the Check Engine Light using an OBDII scanner temporarily fix OBDII code P0721 in a Mazda?

- Resetting the Check Engine Light may temporarily clear the code, but if the underlying issue causing P0721 is not addressed, the code is likely to reappear once the problem resurfaces.

9. Are there any preventive maintenance steps I can take to avoid encountering OBDII code P0721 in my Mazda in the future?

- Regularly inspecting and maintaining the transmission system, checking for fluid leaks, and promptly addressing any unusual shifting behavior can help prevent issues leading to OBDII code P0721 in a Mazda.

10. Can a DIY enthusiast with basic automotive knowledge successfully diagnose and repair OBDII code P0721 in a Mazda?

- While diagnosing and repairing OBDII code P0721 may require some technical expertise, a DIY enthusiast with basic automotive knowledge and the right tools can potentially address this issue, especially if it involves simple tasks like sensor replacement or wiring checks.