Strange Engine Check Light behavior

[91boz]

My 90 240SX engine checklight did something strange today. I started to flash 1 blink..2 blinks.. 3 blinks.. all the way up to 5 blinks and then repeat the cycle again. The engine check light has been on for awhile and last week I tried to retrieve the code from the ECU with no luck. I followed the procedure on this forum turning on the ignition till all the dash lights are on then turning the mode screw clockwise wait 2 secs then counterclockwise but the check lamp did not flash.. Also the mode swich that I turned is labeled rpm.. Is this the right switch or is there another one labeled mode? The one that I turned is an adjustment pot I believe for idle. Can someone steer me in the right direction as to how to get the codes? Also whats up with the flashing check light?