P0729 means Gear 6 Incorrect Ratio. In sixth gear, the computer is seeing an input-to-output speed ratio that does not match sixth gear, which means something is slipping. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0729 means
Electronically controlled automatics are run by a transmission control module (TCM), a separate box or part of the engine computer. It reads speed sensors, the range sensor and fluid temperature to decide when to shift, and drives solenoids that apply clutches and the torque converter clutch. Many basic code readers only show the generic P0700; a scan tool that reads the transmission module shows the specific fault. Check fluid level and condition first, since low or burnt fluid causes many transmission codes.
P0729 symptoms
- Slipping in sixth gear
- Engine revs flare on upshift to sixth
- Limp mode
- Check engine light
Common causes of P0729
- Low or burnt fluid
- Worn clutches for sixth gear
- Pressure control problem
- Faulty speed sensor
How to diagnose P0729
- Check transmission fluid level and condition first
- Check speed sensor readings
- Check line pressure
- Look for other gear ratio codes
Can you drive with P0729?
Limit driving; slipping can quickly damage the transmission.
P0729 tips
Sixth gear is often an overdrive range used at highway speed; slipping there may show first as rising rpm on the highway.
Will P0729 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0729 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0730 | Incorrect Gear Ratio |
| P0735 | Gear 5 Incorrect Ratio |
| P0868 | Transmission Fluid Pressure Low |
Guides that help
When it is more than a sensor
If the fault turns out to be internal (worn clutches, a failed converter or a damaged valve body), compare a rebuild with a replacement in transmission rebuild vs replacement and transmission replacement cost, identify your unit with what transmission do I have?, and browse our transmissions.
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