What does it mean?
P1874 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Select Stroke Sensor Malfunction .
Symptoms
- Malfunction indicator lamp on plus a gearbox warning message on the dash
- Transmission fails to select a gear or gets caught between gates
- Very slow, jerky or incomplete gear changes
- Gearbox drops to neutral while driving and will not re-engage
- Limp operation with limited gears and reduced speed
- Occasionally no drive at all after a restart
Likely causes
- Worn or internally failed select stroke sensor
- Open, short or high resistance in the sensor signal, reference or ground wiring
- Oil or moisture inside the gearbox-mounted connector
- Sensor calibration never performed, or lost after clutch, actuator or battery work
- Select actuator sticking or binding so the shaft never reaches the expected position
- Mechanical wear in the selector mechanism changing the sensor reference points
- Faulty sensor input inside the TCM
How to fix it
- Read TCM codes and freeze frame data before clearing anything
- Watch the select stroke sensor value in live data while cycling through all gates and compare with the commanded position
- Inspect the gearbox connector for oil ingress, corrosion and terminal tension
- Measure sensor supply voltage and ground quality at the connector with the key on
- Check that the select actuator moves freely and the linkage is not binding
- Run the manufacturer-specified calibration or relearn procedure — many faults are calibration, not hardware
- Replace the sensor or the actuator unit if the value stays out of range with good wiring and calibration