P0729
Gear 6 Incorrect Ratio
Transmission gear ratio
Generic OBD-II
High
What it means
P0729 means the transmission control module measured an incorrect ratio between input and output speed in 6th gear — the gear is slipping or not engaging as commanded. It often stems from low fluid, a faulty shift solenoid, or worn internal clutches, and continued driving risks overheating and further transmission damage.
High
Can I keep driving? Drive as little as possible — an incorrect gear ratio means the transmission is slipping or not holding 6th, which can worsen quickly and cause overheating or damage.
Common symptoms
What you'll notice
- Slipping or flaring when 6th gear should engage
- Harsh, delayed, or erratic shifting
- Unable to shift into or hold 6th gear
- Hesitation or jerking on acceleration
- Check-engine light on
Common causes
Most likely first
- Low or degraded transmission fluidLikely
- Worn clutches or internal transmission wearCommon
- Faulty or stuck shift solenoidCommon
- Faulty transmission control moduleLess often
How to diagnose & fix
Work through it in order
- Scan and read freeze-frame, checking for companion solenoid or speed-sensor codes.
- Check the transmission fluid level and condition first.
- Test the shift solenoids and pressure control per service data.
- Inspect for internal wear (clutch/band) if solenoids and fluid are good.
- Repair or overhaul as indicated; replace the TCM only after mechanical causes are ruled out.
FAQ
Quick answers
Is it safe to drive with P0729?+
No — a slipping gear can overheat and damage the transmission fast. Minimize driving until it's repaired.
Can I just clear P0729?+
It returns quickly while the ratio stays wrong; the underlying fluid, solenoid, or mechanical fault has to be fixed.
Related codes
Often seen with P0729
Read & clear P0729 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX