What is a P131 sensor and what does it control? on 1997 Dodge Ram Van 2500

My van is acting like it can't go into any gear except first without a drag at times and then at times its's fine. I had them check it at O'Reillys and their scanner said it was a p131 sensor but they didn't know what that was.

Asked by for the 1997 Dodge Ram Van 2500
2 answers
Ive checked for trouble codes and cant find that code you can check for code numbers at obd-codes.com
02 SENSOR B1 S1 LOW VOLTAGE. NEED TO CHECK THE CIRCUIT AND TEST SENSOR BEFOR JUST REPLACMENT.
COULD BE EITHER CAUSING LIGHT TO COME ON. BUT NOT TRANS. RELATED.