Engine-CodesGMC – P0729 2017 GMC Sierra

P0729 2017 GMC Sierra Code - Transmission 6th Gear Ratio Incorrect

Quick Answer

The P0729 diagnostic trouble code (DTC) for the 2017 GMC Sierra indicates that the transmission's 6th gear ratio is incorrect. Common causes include Low or contaminated transmission fluid, Faulty transmission speed sensor, Wiring or connector issues in the transmission system. 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 2017 GMC Sierra indicates Transmission 6th Gear Ratio Incorrect.
Common causes
Common causes include Low or contaminated transmission fluid, Faulty transmission speed sensor, Wiring or connector issues in the transmission system.
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.
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P0729 2017 GMC Sierra Description

The P0729 diagnostic trouble code (DTC) for the 2017 GMC Sierra indicates that the transmission's 6th gear ratio is incorrect. This means that the signal sent from the transmission control module (TCM) to the engine control module (ECM) regarding the gear ratio in 6th gear does not match the expected value. This discrepancy can lead to various issues with the vehicle's performance, including poor fuel efficiency, rough shifting, and potential damage to the transmission components.

OBDII Code P0729 2017 GMC Sierra - Transmission 6th Gear Ratio Incorrect
P0729 2017 GMC Sierra Code - Transmission 6th Gear Ratio Incorrect

Common Causes of P0729 2017 GMC Sierra

  1. Low or contaminated transmission fluid
  2. Faulty transmission speed sensor
  3. Wiring or connector issues in the transmission system
  4. Malfunctioning TCM or ECM
  5. Mechanical problems within the transmission itself

Symptoms of P0729 2017 GMC Sierra

  1. Hesitation or slipping when shifting into 6th gear
  2. Reduced acceleration and power in 6th gear
  3. Increased fuel consumption
  4. Rough shifting or jerking during gear changes
  5. Illumination of the check engine light

How to Fix P0729 2017 GMC Sierra

  1. Perform a thorough inspection of the transmission system, including checking the fluid level and quality.
  2. Test the transmission speed sensor and replace if faulty.
  3. Inspect the wiring and connectors in the transmission system for any damage or loose connections.
  4. Scan the TCM and ECM for any error codes and address any related issues.
  5. If necessary, rebuild or replace the transmission to correct the gear ratio problem.

Cost to Fix P0729 2017 GMC Sierra

The typical repair costs for addressing a P0729 code on a 2017 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 but does not account for diagnostic time or any additional services that may be required. It is recommended to consult with a qualified mechanic or dealership to obtain an accurate cost estimate based on your vehicle's unique circumstances. Labor rates can vary widely based on location and the type of repair facility, so it is advisable to research local rates for a more precise estimate.

Tech Notes for P0729 2017 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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