Thanks in advance for any help. I will try to be as thorough as possible..
When I open the door to the truck the PCM relay under the dash starts to click on/off (interior lights do the same)..the lights on the dash come on as normal..when I turn the key over the starter relay on the firewall clicks loudly and the starter will not engage. The battery is only 3 months old and I have replaced the starter relay and the PCM relay both this morning with no success. I have a hard time believing the starter would make the PCM relay behave like it is, but I have no clue what to try next. There have been no symptoms of any problems before now. Any suggestions??

 

Have you tried to jump start it? If you do, and it starts, I'd pull the battery and have a parts place run a check on it.

Begin with the easy stuff first. Go from there.

 

x2!