Here guys, this should help clear things up a bit.
"Start Control Box versions:
Older versions are called PCB – Protective Control Box* – They use a Glow Plug Controller instead of a TSU and are generally not favored. Some versions, like the LAU PCBs have been known to start HMMWVs on their own and burn trucks to to the ground.
Then there was the EESS – Engine Electrical Start System – These use TSU.
Newer versions are called S3 – Smart Start System – Also uses TSU.
Not sure what the difference is between EESS & S3. Leave a comment if you know.
KDS Smart Start System (S3) P/N 6500391, CR-2701. NSN 6110015427901. *Replaces P/N 12479192, NSN 6110014912158."
If you want to read the full post go to
http://gear-report.com/help-hmmwv-wont-start-humvee-glow-plug-start-system-maintenance
I would just post pics and whole article here etc but I can't post up pictures for some reason so go check out the link. I trust moderators will not delete this as it has some extremely helpful information for hmmvw owners. This basically solved all problems with ignition on the humvee and is extremely well written imo. So It deserves to be shared with all the members here as you will learn the differences in the boxes etc and problems surrounding them! Have fun!
Ps: I am in no way affiliated with the author or anyone in that link. It was just so well written it needed to be shared with the ss community.