Reddawg750

My 99 Tahoe has the electronic auto tranny and push button 4wd. My tranny is in limp mode and won't shift into overdrive and the speedo is not working. I replaced the VSS(Vehicle Speed Sensor) sensor and it did not fix it. I looked at the wiring loom down to the quick connect and couldn't find anything wrong. I did however find another quick connect just dangling not plugged into anything up by the Trans oil pan and it has the same quick connect end as the one that plugs into the VSS sensor but I can't find anywhare for it to plug into. Please Help!! Any advice will be greatly appreciated.