What it means
The transmission control module detected an incorrect ratio while third gear was commanded or expected. The code alone does not confirm slipping or identify the cause.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The TCM compares input and output speed signals with the ratio expected while third gear is commanded. P0733 sets when that third-gear ratio is outside the allowed range, which can result from fluid, hydraulic, clutch, or speed-signal problems.
Common causes
Most likely first.
- Low or degraded transmission fluid
- Worn or damaged third-gear clutch or friction elements
- Hydraulic pressure loss or valve body fault
- Fault in a speed sensor or its wiring
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and related codes to establish when third gear was commanded and what the vehicle was doing.
- Check fluid level and condition using the manufacturer's specified procedure, since low or degraded fluid can affect third-gear pressure and clutch application.
- Inspect speed-sensor wiring and connectors for damage, contamination, corrosion, or loose terminals.
- Review commanded gear and live input and output speeds during a controlled shift into third gear to see whether the mismatch repeats.
- Test sensor circuits and hydraulic pressure to the manufacturer's specification, then investigate third-gear friction elements and valve-body operation if those checks pass.
Common fixes
- Correct the fluid level or service degraded fluid to the vehicle's requirements.
- Repair damaged speed-sensor wiring or connector contacts.
- Replace a speed sensor if testing shows its signal is inaccurate.
- Repair a confirmed valve-body or hydraulic pressure fault affecting third gear.
- Repair worn or damaged third-gear friction elements if internal inspection confirms the fault.
Can I keep driving?
Avoid towing, hard acceleration, and long drives if the transmission slips or shudders in third gear; seek diagnosis promptly. Continued operation can overheat the fluid and worsen damage to the third-gear friction elements.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.