What is diagnostic code 07020 in a jeep grand Cherokee?

P0720 - Low Output SPD Sensor RPM Above 15 MPH

The relationship between the Output Shaft Speed Sensor and vehicle speed is not within acceptable limits. P0720 - Low Output SPD Sensor RPM Above 15 MPH

Output shaft speed is less than 60 rpm with vehicle speed above 15 mph (4-speed auto. trans. only).