I have a 2004 Ford Explorer sport trac and it would not turn on. The theft light came on and stayed solid (did not blink). When I tried to turn the key nothing would happen at all and the theft light would turn off only to come back on in a few minutes. I was able to start it after using jumper cables. Could this be an issue with the key, and if so, why does it work now, after using the jumper cables? Should I start using the spare key; i have not used that one at all before. Also, could it be a problem with the battery? It is only a little over 1 year old, but should I get it checked out? Thanks for any information.