It's also a really good way to spike (let the smoke out) your BCM/PCM or any other electronic boards and then find the need to replace them. With a DVM across the battery and the truck running measure voltage. Than place a load on the circuit (i.e. headlights on high beams, AC on Max, stereo on) then check V again, it should be a minimum 12.5VDC. If so charging system is good. Then pull battery with truck turned off and take it somewhere to have a a load test performed on the battery. Unless you have a load tester at home.