New member, so excuse my ignorance. I have an '02 excursion that has had a glow plug code for a couple years. It is not hard to start but just with the weather cooling a little if i don't run it for 4-7 days, it doesn't seem to have enough juice to start unless i have it plugged in. My batteries are at 12.6vlt sitting. Would this be a battery issue or glow plug/relay issue and where would i start?