What it means
The transmission control module detected that the transmission remained in sixth gear when another gear was expected. The code does not identify whether the cause is electrical, hydraulic, or mechanical.
At a glance
- Usually lights the check-engine light
How it works
The TCM compares the requested gear with speed-sensor readings to check whether the transmission has reached the expected ratio. P073B sets when sixth gear remains engaged although another gear is expected; it does not by itself identify whether the cause is electrical, hydraulic, fluid-related, or internal.
Common causes
Most likely first.
- Shift solenoid stuck or failed
- Valve body fault affecting sixth-gear shifts
- Low or degraded transmission fluid
- Internal transmission mechanical fault
Symptoms
- Transmission remains in sixth gear or does not shift as expected
- Transmission warning light on
How to diagnose it
- Save freeze-frame data and review commanded gear, actual ratio, and input and output speeds to confirm that sixth gear is being retained.
- Check for related transmission codes that could point to a speed-sensor or shared shift-control fault.
- Look for fluid leaks and check fluid level and condition using the manufacturer's procedure.
- Inspect the transmission harness and connectors for damaged insulation, corrosion, loose terminals, or fluid contamination.
- Compare commanded shift-solenoid states with actual speed changes using a scan tool, then test the sixth-gear-related solenoid, valve body, and internal components as specified.
Common fixes
- Correct low fluid and repair the source of any leak.
- Repair damaged wiring or connector terminals in the transmission control circuit.
- Replace a shift solenoid only if testing confirms it is faulty.
- Repair a valve-body fault affecting sixth-gear control.
- Repair confirmed internal transmission damage if electrical and hydraulic checks pass.
Can I keep driving?
Avoid relying on the vehicle for fast acceleration or driving that requires frequent speed changes while it remains in sixth gear. Stop if the transmission slips, overheats, or becomes unpredictable, since continued driving can worsen damage.
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.