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AutoCodes – Generic – P0731

P0731 Code - Gear 1 Incorrect Ratio

Quick Answer

This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows: Torque converter slip ratio = A x C/B A: Output shaft revolution signal from revolution sensor B: Engine speed signal from Engine Control Module (ECM) C: Gear ratio determined as gear position which TCM supposes If the actual gear position is higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. Common causes include Low transmission fluid level, Dirty transmission fluid, Shift solenoids. 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
P0731 indicates Gear 1 Incorrect Ratio.
Common causes
Common causes include Low transmission fluid level, Dirty transmission fluid, Shift solenoids.
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 100,515
How popular is this code, among other codes? Medium
What is this?
Table of contents Created and updated by William Orellana on May 08, 2019
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Code P0731 Description

This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows:

Torque converter slip ratio = A x C/B
A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined as gear position which TCM supposes

If the actual gear position is higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.
OBDII Code P0731 - Gear 1 Incorrect Ratio - AutoCodes.com
P0731 Code - Gear 1 Incorrect Ratio
What does this mean?

What are the Possible Causes of the DTC P0731?

  • Low transmission fluid level
  • Dirty transmission fluid
  • Shift solenoids
  • Transmission mechanical problems
  • Transmission hydraulic control circuit

How to Fix the DTC P0731?

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 does this mean?

Code Tech Notes

Start by inspecting the transmission fluid level and condition, and change fluid if necessary.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0731 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 P0731 code?

Need more information on how to fix the P0731 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0731 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

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 P0731 Code

No Frequently Asked Questions about P0731 Code found.

Discuss the causes and fixes for P0731 OBDII Code

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  • Goes into first then takes awhile to shift into 3rd have to make shift to 3rd by hitti g the cas
    Peddle or tap up to 3500 rpm cu

    Reply to Comment

    • The P0731 - Gear 1 Incorrect Ratio code means that the transmission control module (TCM) has detected an incorrect gear ratio in 1st gear, which can cause shifting issues, delayed shifts, or slipping. Since your vehicle hesitates before shifting into 3rd gear, it suggests a possible transmission problem related to clutch slippage, fluid pressure, or internal mechanical issues.

      Possible Causes of P0731 and Delayed Shifting:

      1. Low or Contaminated Transmission Fluid

        • Low fluid levels or dirty/burnt fluid can cause shifting delays and incorrect gear ratios.

      2. Worn or Failing Transmission Clutches/Bands

        • If the internal clutch packs or bands for 1st and 3rd gear are worn out, they may not engage properly, causing delayed or erratic shifting.

      3. Faulty Shift Solenoid

        • A malfunctioning shift solenoid may not be directing the correct hydraulic pressure to engage gears smoothly.

      4. Valve Body Malfunction

        • The transmission valve body may have clogged passages or stuck valves affecting the gear engagement.

      5. Torque Converter or Internal Transmission Damage

        • A failing torque converter or internal damage (such as broken gear teeth) can cause an incorrect ratio reading.

      6. TCM (Transmission Control Module) Issue

        • Software issues or electrical faults in the TCM could lead to incorrect shifting behavior.

      Troubleshooting & Fixes:

      1. Check Transmission Fluid:

        • Ensure the fluid is at the correct level and not burnt (dark brown/black with a burnt smell).
        • If the fluid is dirty, a fluid and filter change may help.

      2. Inspect and Test the Shift Solenoids:

        • Using a scan tool, check solenoid performance and transmission pressure readings.
        • If a solenoid is malfunctioning, it may need replacement.

      3. Perform a Transmission Relearn or Reset:

        • Disconnect the battery for 10-15 minutes to reset the transmission adaptive learning.
        • Drive the vehicle smoothly to allow the transmission to relearn shifting patterns.

      4. Check for Other Codes:

        • If additional transmission-related codes (such as P0733, P0734, or P0841) appear, they may provide more clues to the issue.

      5. Test the Torque Converter:

        • If symptoms persist, a failing torque converter could be affecting shift timing and performance.

      6. Consider a Professional Transmission Diagnosis:

        • If the problem continues after checking the fluid and solenoids, a professional transmission specialist may need to inspect the internal components.

      Next Steps:

      If the transmission fluid is good and a reset doesn’t help, I recommend scanning for additional codes and testing the shift solenoids before considering mechanical repairs. If internal damage is suspected, rebuilding or replacing the transmission may be necessary.

      Let us know if you need further guidance!

      Reply to Comment
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