Light on computer?

I noticed my 91 hatch was down on power so I peeled the carpet back and noticed the l.e.d. on the e.c.u. was not on? When I bought the car the light was green, now it's off and when I turn the key on or off it quickly flashes red. Any ideas? How do I check for codes?
Thanks.

count the number of flashes that it gives. then come back

yea, what he said ^ when you turn the key to the on position, the led will blink once to show that it is getting power (a red blink) Then if it starts blinking after that, count how many times it blinks. Count how many blinks in a row untill it pauses for a couple seconds.

i think ur mistaken about it being green when u first got it. That l.e.d. is red and was NEVER green in any 88-91 civic. It should blink once when you turn the key to the ON position. Then if there are any codes it will blink number of times then it will pause.

Maybe I was mistaken but I could have sworn it was green, but upon further research I found that if it were throwing codes the check engine light would be on. Oh well, Now I'm trying to figure out why my car feels like it's down on power? The only power mod I have so far is a cai and it felt faster after I originally installed it. Anything I should look for? Fuel filter? Timing? Also I have a dc 421 header to install later so I want to know what size exhaust I should run? Anyone have pics?
Thanks again