08 Chevy Electrical Issues

I bought a used 08 chevy silverado 1500 2wd with 52000 two months ago and some issues have started showing up. On a good day I turn my truck off the radio still plays untill I open my door, like it should. Then on other days when I turn my truck off it dies, as in all components die, like I disconnected my battery. Before I would try to turn the key and it would start after three to ten tries but latley not so lucky. My response was ok bad battery, went to auto zone, battery tested good. Couple days later same thing happened had to get it towed. Mechanic told me dead battery so we replaced it, cant find anything else. Ok drove for a week it happened again. AAA jumped me took it to the mechanic and nothing was found, no draws on battery AAA guys says since your truck runs it shouldn’t be the alternator. Now today when I parked at work truned the truck off it died, tried to turn the key over a couple times and on the sixth try it turned over. Please help me I am so frustrated I think it is a computer issue.

I would have the alternator tested at autozone just to be sure. From my understanding a bad alternator will kill a good battery. I know thats likely not the problem but just to be positive and rule that out.

Another thought is maybe the ignition switch has gone bad. Something is faulty and not completing the circuit when you turn the key. Intermittent stuff tends to be a worn out or loose connection.

Just on a total whim, if you have a tilt steering column, try seeing if you can start it with the wheel all the way up or all the way down.

We have a 97 expedition whos right turn signal would blink fast like a bulb was going out. We replaced all bulbs and itd still do it. Turned out to “fix” itself with the steering wheel up. Just old wiring that had moved up and down a lot. Im thinking something along those lines could be possible with your ignition switch but its a complete guess.

When you try to start it and it doesn’t start, you turn the key to “start” right? Then what happens? Does it not crank at all? Or does it crank but fails to catch and run?

You seem to indicate the engine will crank over sometime if you make several attempts at turning the key. If so the battery must be charged up and something is wrong within the starter circuit. Most likely just a bad wire connection, hopefully.

There is a starter relay in the fuse panel under the hood that is controlled by the ECM. The ignition switch ties to the BCM module and that ties into the ECM through the data bus line. The Park/Neutral switch ties to the ECU also. Try moving the shift lever around when the trouble happens again to see if that is the trouble. The switch needs to make a ground connection. If that doesn’t help I would check that relay in the fuse panel under the hood. Always check the simpler things first before moving on to the more complex things like the ECU or BCM.

Thanks for the help. The issue is I turn the truck off and its like I disconnected the battery. Some times when I try to start it after this has happened nothing will happen. So I will look into the relays thanks.

Don’t forget to move the shift lever around to see if that makes a difference. The trouble could very well be with the switch for that.