Quick HELP! Truck won't go past 2500 rpm

My son is driving back to Military College from Va to Ga. He's currently near Columbia, SC. He just refueled and said that when he got back on the road his truck refused to go past 2500 rpm. He's got no check engine lights, no stuttering...just sounds like it's hitting a rev limiter. He said the intake/exhaust seems normal. It WILL rev past 2500 in Neutral or Park. He's able to reach highway speeds, but it obviously takes even longer than normal with the RPMs so low. Looking for some quick defferential diagnosis, and maybe some quick checks he can perform while he's on the road.

It's a 2010 V6 Auto, 4wd Base model w/offroad package.

Thanks

 

Has he shut it off and restarted it?
Best I got.

 

Yeah, I believe so. He's planning on stopping again in about 1.5 hours for dinner. I'll have him try and unhook the negative battery terminal for 10-15 minutes to see if it helps.

 

If he finds an open auto parts store a lot will scan for codes for free.

Maybe check the gas cap?

 

Is his ABS light on by chance?

 

I'm not sure about Toyota's, but my wife's CX-5 went into the limp mode from a loose negative cable and then later a weak battery.
Although, she had almost every check light on her intrument panel light up as well.
Once each was corrected her vehicle ran fine.

Hopefully it'll be that simple for y'all.

 

Clean the throttle body and sensor.