Transmission Speed Sensors - What Are They? How Do They Work?

Automatic Transmission Speed SensorWhat do they do?

Measure the rotational speed of transmission shafts.

How do they work?

Input and output transmission speeds are monitored and relayed to the ECM/TCM by an analog or digital signal for proper shift points, speedometer operation and transmission diagnostics.

Where are they located?

Mounted internally or externally on the transmission.

Symptoms of failure

  • Check engine light
  • Poor/erratic shifting
  • No/erratic speedometer operation
  • Transmission limp/fail-safe mode