Engine light on problems?

hi i have a 90 civic dx 1.5 automatic. i have issues with my engine light. after car has warmed up the engine light comes on. also i checked the ecu and it blinks 12 times (12 short blinks) then pauses and again 12 short blinks, and continues the same way. what can it be? need help please thanks. Also the temp guage comes on the half after a while, or are honda like that?