Help me!! Can't safely drive truck..codes P0642..and

[TheWolf]

Sorry it is long, but hard to explain

Here is the problem..was driving the truck a couple weeks ago and it started acting up. was running smarty at the time. truck started bucking and not taking throttle. went back to regular stock software and it acted the same. Thought my lift pump went south.
I have codes P0483 fan speed
P0642 sensor reference voltage 1 circuit low
Drove it today to my grandmothers garage to try changing lift pump, and figured out a little more on how it is acting. It will start and idle fine. But, if you give it throttle it will actually cut the engine out a bit. If you hold the pedal down for a few seconds then it will eventually take some fuel rev up to around 2400rpm and then fall off again. Here is the kicker. If you just touch the pedal ( i mean just touch it enough to very slightly move it) it will take off and rev to around 2400 rpm and take fuel as if nothing is wrong, except it will rev by itself that high with the feather touch of the pedal. Pedal position is probably where you would be normally be around 1000 rpm, but goes to 2400.
I tried unplugging the sensor on the air filter intake to see if it made a difference but it did not. just gave me 2 more codes.

Can anyone help me figure this out and what is the P0642 code??
Thanks in advance