The 'Check Engine' light is on has been for some time,

Ive looked for the Check terminal outside of the truck, near the battery, it has 5 wires? and that switch near the left front speaker... (driver's side) ive flipped it and all it does is cause my Check engine light to go dim, not off...



When i unhook the fuel pump ground which i think goes to the pressure sensor (i might be wrong i dont know)  the 'check engine' light goes off... but it wont start (of course)...

Could the pressure sensor be bad?
Could a new fuel pump be the problem? (they make 2 one from japan *2 grounds* and one from canada *1 ground*)