check engine lamp ON

[HKrpS13]

My check engine lamp poped up the other day so I tried doing the self diagnostic as it says in the chilton manual.
The problem is I don't get it. When do you turn the thing in the back of the computer? Is the key suppose to be in? what position? Could some one tell me step by step.
Thanks in advance

[sanmiam]

have done this lots of times from when the wire on my O2 sensor kept breaking.  The computer is located behind the passenger kick panel.  To remove, remove the one plastic nut by the firewall.  Two body clips then hold it on, so just pull it off with a little force.  The ecu in my s14 is held on with two screws and a nut.  The nut is on the same bolt as the panel, one screw is under the ecu (behind the wires) and the other is obvious.  Twist the ecu so that the little screw and the LED light are facing you.  Now is a good time to make sure your ignition is in the "ON" possition (but not running).  To diagnose follow these instructions:

1)  Turn the screw all the way clockwise and wait a couple seconds.  
2)  Turn the screw all the way back counterclockwise (do NOT force).  The light should start blinking.  The first set of blinks are slow, that number of slow blinks is the first number.  There is a short pause and then the light will blink fast, the number of fast blinks is the second number.  
3)  Put the two numbers together and go to this page:
http://www.zilvia.net/f....t=10141 (http://www.zilvia.net/f/cgi-bin/ikonboard.cgi?act=ST;f=6;t=10141)

To then reset the ECU repeat the above steps, the check engine light should go off until your car senses the problem again (i.e. you did not fix it)  Put all that stuff back together and voila, you saved 70 bucks on getting it diagnosed at the dealership.

P.S.  When looking for #'s of blinks, the check engine light will blink at the same rate as the LED on the CPU
P.P.S.  The check engine light will eventually go away w/o reseting the ecu (given that the problem is fixed) after 50 startups.