Have an 06 with the 4.2l. has about 210k miles.

Just recently when traveling at highway speed in 2HI the lights on the control know go solid for 4HI and blink for the 4LO. The truck runs fine and does not change speed or anything abnormal.
One time it was in the AUTO position and did this and when it was switched to 2HI the lights went out. The last time it happened was in 2HI. It happens about an hour after traveling at speed.
Has anyone had this happen to them? it has been very cold here the last few days this has happened so perhaps that is a factor?
Perhaps something related is that when the truck is in cruise control it has been know to come out of overdrive and the RPMs go from 2k to about 3k then it will come back again just cruising.
I am starting to think it may be a wire harness issue to the trans control. Is there one junction point for the trans and trans case control somewhere that can be easily checked/cleaned.

Otherwise the truck runs great and starts no problem.

 

I had the exact same issue. It was simply the switch on he dashboard that needed to be replaced.

 

That sounds logical. Is that a switch that is easy to replace yourself? or is it a dealership job?

 

Take a look at TSB: PIT3832D: ABS Red Brake SVC And 4WD Light On HVAC Blower Inoperative. Possible ignition switch.

 

Ii had the dealer do it, but that was me. Mine was not the ignition switch as Bern is saying, but the 4wd selection switch