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P0731 2015 GMC Sierra Code - Transmission 1st Gear Ratio Incorrect

Quick Answer

The P0731 code indicates that the Powertrain Control Module (PCM) has detected an incorrect 1st gear ratio within the transmission of a 2015 GMC Sierra. Common causes include Low or contaminated transmission fluid, affecting hydraulic pressure and lubrication, Faulty transmission speed sensors that provide incorrect data to the PCM, Worn or damaged internal transmission components, such as clutches or gears. 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 2015 GMC Sierra indicates Transmission 1st Gear Ratio Incorrect.
Common causes
Common causes include Low or contaminated transmission fluid, affecting hydraulic pressure and lubrication, Faulty transmission speed sensors that provide incorrect data to the PCM, Worn or damaged internal transmission components, such as clutches or gears.
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.
What is this?
Table of contents Created and updated by William Orellana on Oct 01, 2024
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Code P0731 2015 GMC Sierra Description

The P0731 code indicates that the Powertrain Control Module (PCM) has detected an incorrect 1st gear ratio within the transmission of a 2015 GMC Sierra. This code is part of the OBD-II diagnostic system, which monitors various vehicle systems for performance and efficiency. When the PCM identifies that the actual gear ratio does not match the expected ratio, it triggers the P0731 code.

OBDII Code P0731 2015 GMC Sierra - Transmission 1st Gear Ratio Incorrect
P0731 2015 GMC Sierra Code - Transmission 1st Gear Ratio Incorrect

Common Causes of P0731 2015 GMC Sierra

  1. Low or contaminated transmission fluid, affecting hydraulic pressure and lubrication.
  2. Faulty transmission speed sensors that provide incorrect data to the PCM.
  3. Worn or damaged internal transmission components, such as clutches or gears.
  4. Malfunctioning solenoids that control fluid flow within the transmission.
  5. Electrical issues, such as damaged wiring or poor connections, affecting the transmission control module.

Symptoms of P0731 2015 GMC Sierra

  1. Sluggish acceleration from a stop or during low-speed driving.
  2. Engine RPMs increase significantly without a corresponding increase in vehicle speed.
  3. Harsh or erratic shifting, particularly when transitioning from 1st to 2nd gear.
  4. Transmission warning light illuminated on the dashboard.
  5. Unusual noises from the transmission, such as grinding or whining.

How to Fix P0731 2015 GMC Sierra

  1. Fluid Inspection and Replacement: Check the transmission fluid level and condition. If the fluid is low or contaminated, replace it with the manufacturer-recommended fluid.
  2. Sensor Diagnostics: Test the transmission speed sensors for proper operation. Replace any faulty sensors that may be sending incorrect signals to the PCM.
  3. Solenoid Testing: Inspect and test the transmission solenoids for proper function. Replace any malfunctioning solenoids to ensure correct fluid flow and pressure.
  4. Internal Inspection: If the issue persists, perform an internal inspection of the transmission to check for worn clutches or damaged gears. Replace any damaged components as necessary.
  5. Electrical System Check: Examine the wiring and connectors associated with the transmission control module for any signs of damage or corrosion. Repair or replace as needed.

Cost to Fix P0731 2015 GMC Sierra

** The cost to repair a P0731 code can vary widely based on the specific diagnosis and repairs needed. On average, you might expect to pay between $300 to $1,500, depending on whether it involves simple fluid changes or more extensive repairs like replacing internal components. Labor rates typically range from $80 to $150 per hour, with metropolitan areas and dealerships often charging higher rates. Independent shops may offer lower rates. It's advisable to consult local repair shops for a more precise estimate based on your specific vehicle and the nature of the repairs required.

What does this mean?

Tech Notes for P0731 2015 GMC Sierra

Incorrect ratio Diagnostic Trouble Code (DTC) may indicate a component condition with piston seals, clutch plates, or solenoids or it may be caused by a faulty turbine or output speed sensor signal.

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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 P0731 2015 GMC Sierra Code

1. What does OBDII code P0731 mean on a 2015 GMC Sierra?

Code P0731 indicates that the transmission control module (TCM) has detected an incorrect gear ratio in 1st gear.

2. What are the common symptoms of P0731 in a 2015 GMC Sierra?

Symptoms may include difficulty shifting into or out of 1st gear, slipping transmission, reduced acceleration, poor fuel efficiency, and the check engine light being illuminated.

3. What causes the P0731 code in a 2015 GMC Sierra?

Common causes include low or dirty transmission fluid, a faulty shift solenoid, damaged transmission components (like clutches or bands), or a malfunctioning transmission control module.

4. Can low transmission fluid trigger code P0731?

Yes, low or dirty transmission fluid can affect hydraulic pressure and cause incorrect gear ratios, triggering the P0731 code.

5. How do you diagnose the P0731 code on a 2015 GMC Sierra?

Diagnosis involves checking the transmission fluid level and condition, inspecting wiring and connectors, testing shift solenoids, and possibly using a scan tool to monitor transmission data.

6. Can driving with the P0731 code damage my 2015 GMC Sierra?

Yes, continuing to drive with this code can cause further damage to the transmission, leading to more expensive repairs.

7. How do you fix the P0731 code on a 2015 GMC Sierra?

Repairs may include replacing or servicing the transmission fluid, repairing or replacing faulty shift solenoids, fixing damaged gears or clutches, or reprogramming the TCM.

8. How much does it cost to fix the P0731 code in a 2015 GMC Sierra?

Repair costs can vary widely, from $100 for a fluid change to several thousand dollars for transmission rebuilds or replacements.

9. Can a bad speed sensor cause the P0731 code on a GMC Sierra?

Yes, a faulty speed sensor can send incorrect data to the TCM, leading to gear ratio errors and triggering the P0731 code.

10. Is it safe to drive my 2015 GMC Sierra with the P0731 code?

It’s not recommended to drive with this code as it may worsen transmission problems and leave you stranded. Have the issue diagnosed and repaired promptly.

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