P0729 GMC 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 GMC 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.
Code P0729 GMC Description
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.
What are the Possible Causes of the DTC P0729 GMC?
- Low transmission fluid level
- Shift solenoid mechanical fault
- Faulty Turbine Sensor
- Faulty Output Speed Sensor
How to Fix the DTC P0729 GMC?
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.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0729 GMC 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 GMC code?
Need more information on how to fix the P0729 GMC code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0729 GMC code diagnosed by a professional: Find a repair shop in your area
Information for Specific GMC Models
- P0729 2014 GMC Sierra — Transmission 6th Gear Ratio Incorrect
- P0729 2015 GMC Sierra — Transmission 6th Gear Ratio Incorrect
- P0729 2016 GMC Sierra — Transmission 6th Gear Ratio Incorrect
- P0729 2017 GMC Sierra — Transmission 6th Gear Ratio Incorrect
- P0729 2018 GMC Sierra — Transmission 6th Gear Ratio Incorrect
Frequently Asked Questions about P0729 GMC Code
1. What does the OBDII code P0729 mean on a GMC vehicle?
P0729 indicates that the transmission's 6th gear ratio is incorrect, meaning the engine RPM and transmission speed are not aligning as expected in 6th gear.
2. What are the common symptoms of code P0729 on a GMC?
Symptoms include difficulty shifting into 6th gear, slipping gears, reduced fuel efficiency, transmission overheating, or the vehicle going into limp mode.
3. What causes the P0729 code on a GMC vehicle?
Common causes include low transmission fluid levels, a faulty transmission control module (TCM), worn clutches, damaged gear components, or a malfunctioning speed sensor.
4. Can driving with code P0729 damage my GMC vehicle?
Yes, prolonged driving with this code can lead to further transmission damage, reduced performance, and potential safety issues.
5. How can I diagnose the P0729 code on a GMC?
Diagnosis involves checking transmission fluid levels, inspecting the transmission for mechanical wear, testing the speed sensors, and scanning the TCM for additional related codes.
6. Is low transmission fluid a possible cause for the P0729 code?
Yes, insufficient transmission fluid can disrupt gear engagement and cause the 6th gear ratio to be incorrect.
7. How can I fix the P0729 code on my GMC vehicle?
Repairs may involve replenishing or flushing transmission fluid, replacing faulty sensors, repairing or rebuilding the transmission, or reprogramming the transmission control module.
8. How much does it cost to repair code P0729 on a GMC?
Repair costs vary widely depending on the issue, ranging from $100 for fluid replacement to several thousand dollars for transmission rebuilds or replacements.
9. Can a faulty transmission control module cause code P0729?
Yes, a malfunctioning TCM can fail to properly control gear ratios and result in the P0729 code.
10. Does clearing the P0729 code fix the problem on a GMC?
No, clearing the code without addressing the underlying issue will not fix the problem, and the code is likely to return.
Discuss the causes and fixes for P0729 GMC OBDII Code
Code P0729 GMC comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
