2000 f150 4.2L V6. I went to start it the other day and only got a single click. Lights worked just wouldn't start. So I started with the obvious. Checked the battery and terminals. They were clean and the battery is good (had it tested twice). Moved on to the starter. Took it in and had it tested, came back good. Thought it might be the hot wire running to the starter because of some corrosion, so I replaced that. Still nothing. Replaced the the starter switch (or starter relay, I've heard it called both) on the firewall, still wouldn't start. Tried the screwdriver trick to check the ignition and it didn't work so the ignition is good. Other than having the starter checked again, I'm not sure where to check next, any suggestions? It ran/started well the night before with no indication of a problem. Thanks!

 

Have you tried jumping it?

 

The battery? Yes, but i haven't tried jumping the starter yet because i had it tested but i was planning on trying that tonight.

 

I had the same problem. Jumped underneath and a wire had actually corroded so badly that it ate it in 2 pieces and the starter was still reading good. Might need to go underneath and check the actual starter wire yourself. Computers aren't as good at problem solving as smart people are... Even when it says something is good it could be bad.