I bought this inexpensive (cheap) tpms system from Amazon:  Amazon.com: KKmoon Solar Energy TPMS, Tire Pressure Monitoring System with 4 Internal Sensors Alarm Function, Wireless Real-time Display 4 Tires' Pressure & Temperature with Clear LED Display: Automotive

It has the capability to monitor five sensors, but came with four sensors.  I am trying to figure out how to get a fifth to program to it.  My problem is that I don't know what 'vehicle' to select.  I've already tried the latest firmware and all the 'retrofit' options without success.  

The sensors have nothing on them other than stickers indicating which tire they should be placed in.  

Anyone have any tips that I can try?