I have a 2001, 4.6, 4x4, Supercrew F-150. The truck runs nice, never had a problem with it until today. I drove north about an hours away, and parked the truck to go fishing. Everything is fine. Started up no problem when I was leaving to hit another spot. Parked, and when I left, and tried starting it, the first thing I noticed was when I turned the key to on, I think it's the solenoid that started clicking, then I noticed that all my dash gauges bottomed out high (like when you reset the computer, or reconnect the terminals to the battery) I turned the key again, and it works. I drive an hour back home, stop at a store, try to start, and nothing. It clicked, but then it was the like the battery was dead, but it's not cause when I go to ATT, the radio still comes on. It still bottoms out high. I get NO SERVICE ENGINE LIGHT. No Warning. I played with all the wires under the hood and after trying to start it atleast 30 times, finally, luckily, it started. I went home, turned it off, and tried starting it. All I get are the clicks, the alarm light on the dash flashes constantly, gauges still bottom out, after a while nothing worked. No power whatsoever. Played with the battery, still nothing. Then, somehow, I got power back to the inside, but when I go to try and start it, it keeps resetting itself, then all the power goes out, and when the drivers side door is open, the alarm light flashes, and in the fuse/relay box inside the cab, relay #2 is clicking. I checked all my fuses, and they're still in tact, checked all the wires under the hood that's visible to me, they're all good, pressed the relays, and fuses to see, if maybe one had come loose, they're all good. I get like a 50/50 shot of the truck starting. I have no idea what it is. Relay #2 is the PCM (Powertrain Control Module) Relay. Can anyone help me???

 

I had something similar on my 06 when it only had 3500 miles.
I took it to the dealer and found that the battery was defective.
Maybe the post connection inside is bad giving it intermittent problems

 

Most likely, you have a bad battery cable or connection.

Get an assistant to turn the key and a digital voltmeter.

Connect a digital voltmeter across what should be a solid, direct connection and watch the meter while the starter is engaged. A faulty connection or cable will show a voltage reading greater than 1/4 volt, even up to the bulk of the battery voltage. A good connection will show less than 1/4 volt of drop. Repeat this test at the battery terminals to check for a bad battery or internal fault.

Steve