What it means
The transmission control module detects a performance fault in its internal transmission speed-sensor function.
At a glance
- Usually lights the check-engine light
How it works
The TCM processes transmission speed-sensor information to determine how fast transmission components are turning and to support shift control. This code sets when the TCM’s internal speed-sensor processing does not perform as expected, even if the underlying sensor signal or module power and wiring may be involved.
Common causes
Most likely first.
- TCM internal speed-sensor processing fault
- TCM power, ground, or wiring fault
Symptoms
- Transmission warning light
- Erratic or harsh shifts
- Limited shifting or limp mode
How to diagnose it
- Save freeze-frame data and scan for other transmission codes to determine whether the fault occurred with a missing speed signal, a power interruption or a related shift problem.
- Check live input and output speed data at idle and during a cautious drive, looking for readings that drop out, remain fixed or conflict with vehicle speed.
- Inspect TCM and transmission connectors, harnesses, battery connections and grounds for looseness, corrosion, damage or fluid intrusion.
- Check TCM power and ground under the conditions specified by the manufacturer, since voltage loss or a poor ground can disrupt internal signal processing.
- If external circuits and available speed signals check out, use the manufacturer’s diagnostic procedure to assess the TCM’s internal speed-sensor processing.
Common fixes
- Clean and secure a loose or corroded TCM or transmission connector.
- Repair damaged wiring, power supply connections or grounds to the TCM.
- Repair an identified external speed-signal fault if live data or related codes point to one.
- Replace or reprogram the TCM only if its power, ground and external circuits pass the specified checks and internal processing is confirmed faulty.
Can I keep driving?
If shifting is erratic or limited, avoid high speeds, heavy loads and situations that require predictable acceleration; the transmission may enter limp mode or lose normal shift control. Stop driving if it slips badly or cannot maintain drive.
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.