This is a quick and technical answer. Your 2006 engine is electronic, your pump panel is also. Many things must be set correctly for the pump to go in gear and the throttle go active. The park brake must be applied. The pump shift lever needs to be in "pump" and the pump shift has to actually happen and activate a sensor on the outside of the fire pump.. If this happens a green "pump shift" light will go on in the cab and on the pump panel. Then the trany needs to be put into "drive". The electronic trany will sense the pump shift has occured and go directly into 4th gear. On a touch pad control with two windows it will show 4 & 4. If the pump shift hasnt occured the windows will say 1 & 4. If the trany actually makes it into 4th gear the second green light "ok to pump" goes on and the throttle controls on the pump panel go active. Some manufacturers add more steps (interlocks) that add a step like having to push the tranny mode button but this is the basic circuit. At what point does your engine not do what I have described?
99 Piece Saber pumper same problem. And I believe at my full time dept now we have 2 97s same problems some times but I think our mechanics fixed it, Chief we have 3 KME's I don't like them we are getting a new mid mount Tower ladder 100ft this month from KME I heard they are a really good TL since whoever they bought out, it was suppose to be a FDIC show truck but we got screwed out of that but we are still getting the bells and whistles that were put on it for the show from what I have heard... The engine I am in is an 09 Sutphen LOVE IT!
You may want to check the electronic relay/transfer switch between the engine and the pump. My former dept had this issue with one of their trucks. I’ll check with them to get the exact reason for you. I believe it ended up being an $80.00 part.
A second possibility is that the last time you used the pump, your pump operator did not throttle the pump down to idle before switching back to the engine. This will keep you from being able to switch back into pump gear until you have throttled back down from the pump throttle control (simply put your revs are to high for the engine transmission to switch without causing major transmission problems)
We had a similar problem with our 08 Pierce. Turned out to be the electronic touch pad was bad. Is it normal to have to push and hold the increase button for awhile before it starts to throttle up? Ours still seems to take forever to increase RPM's, but idles down almost instantly.