I am new to this site and honestly, I really have no idea if I'm posting this in the right area.
I have a 2004 Yukon Denali with 145k miles and have never had any issues with it. It'* been a great vehicle for the family. However, recently, it'* had some battery related issues. If I let it sit in the garage for a day or two, the battery is always dead. I charge it or give it a jump and it starts right up. Today I took it out and when I went to stop for a train, it started to shake a bit, the lights dimmed and it shut off. So I put it in park and started it up again. I took it straight to o'reilly auto parts where they tested both the battery and the alternator. Both tested out to be good. The employee told me that the fuel filter probably needs to be changed and reccomended that I put some Seafoam in the gas tank. On the way home, everything was working fine (Note that I hadn't put the Seafoam in yet, I was going to do it once I got home). Even when I stopped, everything seemed normal. So now I'm stuck here wondering if it'* a fuel issue or a battery issue. I do know that the battery is fairly old and probably needs to be changed anyway. Also, it has been extremely cold here.. ranging from -2 to 12 F and my battery seems to have more issues the colder it is. Could the vehicle have just died because of the cold weather and then worked fine after the engine had warmed up? Could the fuel pump be going out?
TIA everyone. Sorry if this post sounds like an obvious fix. I'm not exactly car savvy and am a complete worry-wart.