AutoCodes – GMC – P0729 2016 GMC Sierra

P0729 2016 GMC Sierra Code - Transmission 6th Gear Ratio Incorrect

Quick Answer

The transmission turbine speed sensor and vehicle speed sensor are hall-effect sensors. Common causes include Low transmission fluid level, Shift solenoid mechanical fault, Faulty Turbine Sensor. 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 2016 GMC Sierra indicates Transmission 6th Gear Ratio Incorrect.
Common causes: Common causes include Low transmission fluid level, Shift solenoid mechanical fault, Faulty Turbine Sensor.
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 196

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 29, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0729 2016 GMC Sierra Description

The transmission turbine speed sensor and vehicle speed sensor are hall-effect sensors. The turbine speed sensor is mounted to the transmission housing and faces the reluctor attached to the 1-2-3-4-5-6 clutch piston housing. The vehicle speed sensor is mounted to the low and reverse clutch housing on 2WD, or transfer case rear case half on 4WD. The vehicle speed sensor faces a reluctor wheel attached to the transmission output shaft on 2WD, or a reluctor wheel attached to the transfer case rear output shaft on 4WD.
The TCM provides a 9 V reference circuit and a signal circuit to each of the sensors. As the 1-2-3-4-5-6 clutch piston housing and transmission output shaft or transfer case output rotates, the sensors produce a signal frequency based on the teeth on the reluctor wheel. The TCM calculates the transmission gear ratio based on the speed sensor signals and compares the calculated gear ratio to the commanded gear ratio.
The Diagnostic Trouble Code (DTC) will be set when the TCM detects the calculated gear ratio with 6th gear commanded differs from the known 6th gear ratio for 2 s.

OBDII Code P0729 2016 GMC Sierra - Transmission 6th Gear Ratio Incorrect - AutoCodes.com — P0729 2016 GMC Sierra Code - Transmission 6th Gear Ratio Incorrect

What does this mean?

What are the Possible Causes of the DTC P0729 2016 GMC Sierra?

Low transmission fluid level
Shift solenoid mechanical fault
Faulty Turbine Sensor
Faulty Output Speed Sensor

How to Fix the DTC P0729 2016 GMC Sierra?

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

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0729 2016 GMC Sierra 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 P0729 2016 GMC Sierra code?

Need more information on how to fix the P0729 2016 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 P0729 2016 GMC Sierra Code

1. What does the OBDII code P0729 mean on a 2016 GMC Sierra?

P0729 indicates that the transmission control module (TCM) has detected an incorrect gear ratio in 6th gear, suggesting a potential issue with the transmission or related components.

2. What are the common symptoms of a P0729 code on a 2016 GMC Sierra?

Symptoms include poor acceleration, slipping in 6th gear, decreased fuel efficiency, harsh shifting, or the transmission failing to engage 6th gear.

3. What causes the P0729 code on a 2016 GMC Sierra?

Common causes include a faulty transmission solenoid, worn clutch packs, low or dirty transmission fluid, a malfunctioning transmission control module, or mechanical damage inside the transmission.

4. Can low transmission fluid cause the P0729 code on a 2016 GMC Sierra?

Yes, low or contaminated transmission fluid can affect hydraulic pressure and lead to gear ratio issues, triggering the P0729 code.

5. How is the P0729 code diagnosed on a 2016 GMC Sierra?

A technician will use a scan tool to check for additional trouble codes, inspect the transmission fluid, test the operation of the transmission solenoids, and potentially perform a road test to monitor gear ratios.

6. Can I drive my 2016 GMC Sierra with the P0729 code?

Driving with the P0729 code is not recommended, as it can cause further damage to the transmission and lead to unsafe driving conditions.

7. What repairs can fix the P0729 code on a 2016 GMC Sierra?

Repairs may include replacing a faulty shift solenoid, flushing and refilling the transmission fluid, repairing or replacing damaged internal transmission components, or reprogramming the transmission control module.

8. How much does it cost to repair the P0729 code on a 2016 GMC Sierra?

Repair costs vary depending on the cause, ranging from $100 to $400 for a solenoid replacement to several thousand dollars for a full transmission rebuild or replacement.

9. Can a faulty speed sensor cause the P0729 code on a 2016 GMC Sierra?

Yes, a malfunctioning input or output speed sensor can provide incorrect data to the TCM, leading to a gear ratio error and triggering the P0729 code.

10. How can I prevent the P0729 code from occurring on my 2016 GMC Sierra?

Regularly maintaining the transmission, including fluid changes, checking for leaks, and addressing any minor transmission issues promptly, can help prevent the P0729 code.