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P0729 2014 GMC Sierra Code - Transmission 6th Gear Ratio Incorrect

Quick Answer

The P0729 diagnostic trouble code (DTC) for a 2014 GMC Sierra indicates that the transmission's 6th gear ratio is incorrect. Common causes include Worn transmission components: Wear and tear on transmission gears, clutches, or bands can lead to an incorrect gear ratio, Faulty transmission speed sensor: A malfunctioning speed sensor can provide inaccurate data to the ECM, leading to the incorrect gear ratio, Transmission fluid issues: Low or contaminated transmission fluid can affect the transmission's ability to shift properly. 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
P0729 2014 GMC Sierra indicates Transmission 6th Gear Ratio Incorrect.
Common causes
Common causes include Worn transmission components: Wear and tear on transmission gears, clutches, or bands can lead to an incorrect gear ratio, Faulty transmission speed sensor: A malfunctioning speed sensor can provide inaccurate data to the ECM, leading to the incorrect gear ratio, Transmission fluid issues: Low or contaminated transmission fluid can affect the transmission's ability to shift properly.
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 Sep 16, 2024
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Code P0729 2014 GMC Sierra Description

The P0729 diagnostic trouble code (DTC) for a 2014 GMC Sierra indicates that the transmission's 6th gear ratio is incorrect. This means that the Engine Control Module (ECM) has detected a discrepancy between the expected gear ratio in 6th gear and the actual gear ratio being achieved by the transmission. This issue can lead to poor fuel efficiency, reduced engine performance, and potential damage to the transmission if left unaddressed.

OBDII Code P0729 2014 GMC Sierra - Transmission 6th Gear Ratio Incorrect
P0729 2014 GMC Sierra Code - Transmission 6th Gear Ratio Incorrect

Common Causes of P0729 2014 GMC Sierra

  1. Worn transmission components: Wear and tear on transmission gears, clutches, or bands can lead to an incorrect gear ratio.
  2. Faulty transmission speed sensor: A malfunctioning speed sensor can provide inaccurate data to the ECM, leading to the incorrect gear ratio.
  3. Transmission fluid issues: Low or contaminated transmission fluid can affect the transmission's ability to shift properly.
  4. ECM software issues: Software glitches or programming errors within the ECM can cause the incorrect gear ratio to be detected.

Symptoms of P0729 2014 GMC Sierra

  1. Decreased fuel efficiency: The incorrect gear ratio can lead to the engine working harder than necessary, resulting in decreased fuel efficiency.
  2. Slipping transmission: The transmission may slip or struggle to shift into 6th gear properly.
  3. Engine misfires: The engine may experience misfires or hesitation when trying to maintain speed in 6th gear.
  4. Check Engine Light: The Check Engine Light may illuminate on the dashboard to indicate the presence of the P0729 code.

How to Fix P0729 2014 GMC Sierra

  1. Diagnose the issue: Use a scan tool to retrieve the DTC and perform a thorough inspection of the transmission components and sensors.
  2. Check transmission fluid: Ensure that the transmission fluid level is correct and that it is clean and free of debris.
  3. Replace faulty speed sensor: If the speed sensor is found to be faulty, replace it with a new one.
  4. Repair or replace transmission components: If worn components are identified as the cause, repair or replace them as needed.
  5. Clear codes and test drive: Clear the DTC from the ECM, test drive the vehicle to ensure the issue is resolved, and verify that the correct gear ratio is being achieved.

Cost to Fix P0729 2014 GMC Sierra

The typical repair costs for addressing a P0729 code on a 2014 GMC Sierra can range from $200 to $800, depending on the specific cause of the issue and the extent of the repairs needed. This estimate includes parts and labor. It's important to note that diagnosis time and labor rates at auto repair shops can vary, so it's advisable to check with local shops for a more precise estimate based on your location and vehicle details.

What does this mean?

Tech Notes for P0729 2014 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.

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