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Summary
  • Diagnostic trouble code (DTC) P0731 stands for “Gear 1 Incorrect Ratio.” This code implies that the transmission is slipping. The powertrain control module (PCM) detects that the revolutions per minute (RPM) difference between the rotational speed of the two sensors in Gear 1 falls outside the normal range.
  • Common causes for the P0731 code include a defective gear 1 shift solenoid, internal transmission failure, and a defective speed sensor.
  • Symptoms of the P0731 code include an illuminated check engine light, the vehicle not shifting properly, and decreased fuel economy.

One of the diagnostic trouble codes that you might encounter is the P0731 code. This is one of the thousands of codes that may be logged by different makes and models. However, the methods for testing and fixing this code may differ among auto manufacturers.

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Here is some generic information about the P0731 code that may help you understand the common triggers and symptoms of this OBD-II code.

What Does the P0731 Code Mean?

Diagnostic trouble code (DTC) P0731 code stands for “Gear 1 Incorrect Ratio.” This trouble code implies that the transmission is slipping. It may happen while the driver is shifting gears or while driving at steady speeds in the same gear.

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The P0731 code is set when the values from the transmission input and output speed sensors do not correlate.

The operation of the transmission and its components is monitored by the powertrain control module (or the transmission control module) with the help of input from various sensors. Two of these sensors are the transmission input speed sensor and the transmission output speed sensor.

The readings from the transmission input and output speed sensors are compared to determine gear ratio and torque converter slip. When the powertrain control module (PCM) detects that the RPM difference between the rotational speed of the two sensors in Gear 1 falls outside the normal range, the P0731 code is set.

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If you’re planning to fix P0731 yourself, our technical discussion about OBD codes and gear ratios can help you come up with a proper solution.

Note: The definition of code P0731 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0731 Code?

  • Defective Gear 1 Shift Solenoid
  • Internal transmission failure
  • Defective speed sensor
  • Defective Valve Body
  • Dirty transmission fluid that restricts the hydraulic passages
  • Low transmission fluid level

What are the Common Symptoms of the P0731 Code?

How to Diagnose the P0731 Code

Identifying the underlying cause of the P0731 code can be difficult, especially if you’re not confident with your automotive knowledge. In most cases, it would be best to bring your vehicle to an auto repair shop and seek the help of a professional for an accurate diagnosis. Otherwise, you should refer to the manufacturer’s repair information when troubleshooting this code.

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difficulty shifting gears
Difficulty changing gears is one of the common symptoms of the P0731 code.

How to Fix the P0731 Code

The P0731 code is a generic trouble code that may apply to various makes and models. While vehicles from different manufacturers may share common symptoms, the steps for diagnosis and repair for a P0731 Ford code may differ from a P0731 Jeep code.

If you’re an advanced DIYer who’d like to fix this code on your own, it will be helpful to refer to your repair manual or get factory vehicle repair information from an online subscription service or a repair manual.

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About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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