really bad problem

ok, my mph gauge went out! this really sucks. just for shits and giggles i run for codes, when i put my code key in (that i got from autozone, it was free) anyway im not stupid i ran for codes before and stuff. but this time the thing wont even blink "12" it just comes on for about 1/4 for a second and goes off.
also when i turn my car to the "on" position without starting it, the fan comes on for about 30 seconds. i dont know whats going on. could someone pls help me!

thx!

if i am not mistaken when u turn the car to the "on" position with a code reader in the fan is supposed to come on, and its possible that the reason no codes are flashing is that u dont have any

ya i mean the fan come's on when the code key isnt in the fuse box. i mean just put it in the "on" position and it comes on. its really weird

oh and also my speed-o dosnt work and my trip milage and my total milage dosnt work when im driving.

Sounds like speed sensor bad.

the fan stays on untill i crank it. btw