What it means
While in 10th gear, the measured input/output ratio does not match the calibrated value.
At a glance
- Usually lights the check-engine light
How it works
The transmission control module compares the transmission’s input and output speeds to check whether 10th gear is delivering its expected ratio. This code sets when the measured ratio while 10th gear is commanded falls outside the calibrated range, which can happen if a friction element slips or a speed signal is wrong.
Common causes
Most likely first.
- Internal clutch or friction element slipping
- Low or degraded transmission fluid
- Hydraulic pressure loss or valve body fault
- Incorrect input or output speed sensor signal
- Internal transmission wear or damage
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 review commanded gear, input speed, output speed, and transmission temperature to see when the 10th-gear ratio error occurred.
- Check the fluid level and condition using the vehicle maker’s specified procedure, since low or degraded fluid can reduce clutch holding and hydraulic pressure.
- Inspect the transmission connectors and wiring for loose connections, corrosion, or damage that could distort the input- or output-speed signal.
- Compare live input- and output-speed readings during a suitable road test with the commanded gear, and check for implausible or dropping signals.
- If the speed signals and fluid are sound, have hydraulic pressure and valve-body operation checked against the manufacturer’s procedure.
- If pressure is adequate but the ratio still slips in 10th, investigate the relevant internal clutch or friction elements for wear or damage.
Common fixes
- Correct the fluid level or address a leak, using the specified fluid and service procedure.
- Repair damaged wiring or connectors affecting the input- or output-speed sensor signals.
- Replace a confirmed faulty input- or output-speed sensor.
- Repair a verified valve-body or hydraulic pressure fault.
- Repair or rebuild the transmission if its 10th-gear friction elements are worn or damaged.
Can I keep driving?
Avoid towing, hard acceleration, and continued high-speed driving if the transmission slips, shudders, or shifts harshly; slipping can quickly worsen clutch damage. If it loses drive or enters limp mode, stop somewhere safe and arrange recovery.
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.