sounds like you Focked up when you took it out...I would guess that you need to go a salvage yard and get another one...then if your truck is still under warrantee go to the dealer and have the check it out...they will clear the codes then remove the next one with EXTREME caress....and don't touch the needles in the sensor...
i have took it off before when i put my k&n gen 2 on, i figured out when i put the maf back on, that i put it back on upside down and backwards, ran it like this for about 10 miles, got back realized the mistake, so put screen back on and put maf back on right, light still on! what should i do!!!!!! xtreme21
Or, take a paper clip and bend it like a U. Put one end of the paperclip into the top left slot and 3 over (3rd slot) and the 2nd end of the paperclip on the top row 8th plug over. Your service engine light will blink a few times. Count how many times it blinks and call a dealer, or get an OBD II book and it tells you what is wrong. Probably just tinkered with a sensor. I already have an OBD II scanner but just found out about the paperclip trick. Its amazing how much they charge for those POS's and all it does is read electronic pulses from your CPU.
I would say unhook your battery first, let the CPU clear itself. Then reconnect, if the light is still on then try my idea and see what sensor was tripped. After that, then just goto the dealer, if they are *****es, then get a junk yard one, or GMAF!