clearing codes

.....possible? i cant seem to find any info in shop manuals or OTC manuals of how to clear the computer codes.... i kinda messed up and disconnected some sensors with the ignition on or the engine running and now im getting too many codes, some of which indicate bad sensors that i just replaced (prior to screwing up codes) like the coolant temp sensor and such....

think i might need a new ECA cuz ive replaced just about every other component of the EEC-IV, save a few sensors and actuators, and my problem still hasnt been solved. thanks for your help guys

ok thanks a lot, i tried disconnecting the battery for 30 sec. i thought that was the time to clear it but ill just do the 20 mins thing, thanks again