Got a 01 5.9L and goodness I'm at a loss now. I replaced the battery and also the starter and everything has been great until today. I got in and turned the key only to hear a sound like the battery was dead. I gave it a little gas and it started but when I let off the gas it died. I figured a jump would work but the truck still dies after it starts unless I tap the gas. Kept on til it finally got me home then abruptly died. Also, when it dies my O/D off light comes on and stays on til I turn it off. Not sure if that matters at all. Battery reads 12.6 on my meter when not running and 13.5 when it's running so I feel like it's not my alternator. Can anyone please help?? Thank you in advance!

 

Pull the battery and have it load tested. My truck does pretty much the same thing when it's toast.

For what it's worth, I'm fighting with mine draining the battery when I leave it sit too long unless I disconnect it. I've killed 3 batteries in the last few years and I still can't find the problem.

 

Check your battery cables. Especially your ground cable. I don't mean just at the battery, but at both ends. I've seen bad grounds that were so corroded they fell apart at the frame ground. Resistance goes up until they melt in two.

 

Thank you so much! At least I'm not alone and I have a direction to go in.

 

Grounds down low never really get checked. I had one corrode so much that one time I tried to start the car, it was so thin the amperage melted it apart. If you ever look at police cars, they often have extra grounds. They reduce static but also let electricity flow easily.