P0731 Code: Gear 1 Incorrect Ratio

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.

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.

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.

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?

• Check Engine Light will illuminate
• Vehicle will not shift properly
• Decrease in fuel economy
• Whining noise from the transmission pump
• Vehicle stuck in “limp mode”
• Vehicle will not move

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.

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 Fordcode may differ from a P0731 Jeepcode.

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.

Products Mentioned in this Guide

Speed Sensor Engine Control Module Valve Body