What it means
The TCM cannot read a valid position signal from shift fork A position sensor. Selector engagement state is unknown.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Shift fork A moves a transmission selector to engage a gear, and its position sensor reports that movement to the TCM. The TCM sets this code when it cannot read a valid signal from the shift fork A position circuit, leaving the fork’s engagement state uncertain. The resulting control problem can delay or prevent shifts.
Common causes
Most likely first.
- Position sensor failed
- Wiring or connector fault
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
- Read transmission codes and freeze-frame data, then check live data for the shift fork A position signal and whether it changes as the TCM commands movement.
- Inspect the shift fork A sensor connector and accessible wiring for looseness, corrosion, damage, or fluid intrusion.
- Check the sensor supply, ground, and signal circuit using the manufacturer’s wiring diagram and electrical procedure.
- Test continuity and look for shorts or poor terminal contact in the shift fork A position circuit.
- If the circuit checks pass, test the shift fork A position sensor and selector mechanism using the manufacturer’s procedure.
Common fixes
- Reseat or repair a loose or damaged shift fork A sensor connector.
- Repair an open, shorted, or corroded wire in the position circuit.
- Replace the shift fork A position sensor if it fails the prescribed test.
- Repair a selector or fork mechanism fault if the sensor circuit works but fork movement is not reported correctly.
Can I keep driving?
Limit driving and avoid high-speed trips because the TCM may not know whether shift fork A is engaged, and the transmission can miss shifts or enter limp mode. Stop if the vehicle cannot select or hold a gear reliably.
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.