AutoCodes – Generic – P1721

P1721 Code - Gear 1 Incorrect Ratio

Quick Answer

The vehicle speed sensor·MTR signal is transmitted from combination meter to Transmission Control Module (TCM) by CAN communication line. Common causes include Faulty Vehicle Speed Sensor, Vehicle Speed Sensor harness is open or shorted, Vehicle 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: P1721 indicates Gear 1 Incorrect Ratio.
Common causes: Common causes include Faulty Vehicle Speed Sensor, Vehicle Speed Sensor harness is open or shorted, Vehicle 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 32,666

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 Sep 12, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1721 Description

The vehicle speed sensor·MTR signal is transmitted from combination meter to Transmission Control Module (TCM) by CAN communication line. The signal functions as an auxiliary device to the revolution sensor when it is malfunctioning. The TCM will then use the vehicle speed sensor·MTR signal.

OBDII Code P1721 - Gear 1 Incorrect Ratio - AutoCodes.com — P1721 Code - Gear 1 Incorrect Ratio

What does this mean?

What are the Possible Causes of the DTC P1721?

Faulty Vehicle Speed Sensor
Vehicle Speed Sensor harness is open or shorted
Vehicle Speed Sensor circuit poor electrical connection
Transmission Control Module (TCM) communication

How to Fix the DTC P1721?

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 P1721 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 P1721 code?

Need more information on how to fix the P1721 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1721 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1721 Ford — Gear 1 Incorrect Ratio
P1721 Hyundai — Control Relay
P1721 Infiniti — Vehicle Speed Sensor MTR
P1721 Nissan — Vehicle Speed Sensor MTR

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 P1721 Code

1. What are the common symptoms of OBDII code P1721 (Gear 1 Incorrect Ratio)?

The common symptoms of P1721 include harsh or delayed shifting, slipping gears, poor acceleration, and illuminated Check Engine Light.

2. What causes OBDII code P1721 to trigger?

P1721 is typically triggered by issues such as low transmission fluid level, faulty transmission solenoids, a malfunctioning transmission control module, or mechanical problems within the transmission.

3. How serious is OBDII code P1721 (Gear 1 Incorrect Ratio)?

P1721 can lead to further damage to the transmission if left unresolved. It is advisable to address this issue promptly to prevent costly repairs in the future.

4. Can driving with OBDII code P1721 cause any harm to the vehicle?

Continued driving with P1721 may result in decreased fuel efficiency, poor performance, and potential damage to the transmission components. It's recommended to address the issue as soon as possible.

5. What are some DIY repair tips for OBDII code P1721?

DIY repair tips include checking transmission fluid levels, inspecting for leaks, ensuring proper electrical connections, and performing a reset of the transmission control module.

6. How can a mechanic diagnose OBDII code P1721?

A mechanic would typically use a scan tool to retrieve the trouble codes, perform a visual inspection of the transmission components, conduct a road test to observe the shifting behavior, and possibly inspect the transmission fluid condition.

7. Is it safe to continue driving when OBDII code P1721 is present but the symptoms are not noticeable?

While it may seem safe if symptoms are not present, it's still advisable to address the underlying issue promptly to prevent potential damage to the transmission and ensure the vehicle's optimal performance.

8. Are there any recalls related to OBDII code P1721?

Recalls related to P1721 may vary by vehicle make and model. It's recommended to check with the manufacturer or a dealership to see if there are any recalls that apply to your specific vehicle.

9. How much does it cost to repair OBDII code P1721?

The cost of repairing P1721 can vary depending on the underlying issue. It's best to consult with a mechanic to diagnose the problem accurately and provide an estimate for the necessary repairs.

10. Can OBDII code P1721 be cleared/reset without fixing the underlying issue?

Clearing the code without addressing the underlying problem will only temporarily remove the Check Engine Light. The issue causing P1721 will persist, potentially leading to further complications down the line.