The only component left to check is the AT Neutral position Backup Lamp Switch on the tranny

 

Don't forget to check fusable links and Ignition Switch. Mine did same with a bad Ignition Switch.

 

First Day I have had time to troubleshoot.

Verified 12V at Relay from Ignition switch (yellow wire)
Chacked for voltage from Neutral Safety Switch (Black/yellow stripe) there was 0 volt

Replaced Neutral Safety/Back up Switch

YEAH!!! Truck started!!!!!!!!

 

Good Job.

Apperently just "good job" is too short to post, so: I commend you on your persistence and diligence which has led to the ultimate successful resolution of this problem.

 

Now the question of the day:

What is the purpose of the signal From the PMC to the Starter relay? It is connected to the same terminal as the Back up/Neutral Safety Switch

 

I dont have any square relays on my fender

 

I have a 2015 2500 6.7 turbo with No Start.. Starter is good, batteries are good. Engine tries to crank but doesn't. If I jump directly to solenoid to activate starter it cranks fine. What am I missing? Solenoid activation circuit seems to be the suspect.

 

You would probably have better luck starting your own thread in the 4th gen section