How do you read the PCM codes for a 1987 Chevy Celebrity?

TAke a paper clip or other wire and short "A"&"B" terminals together on the aldl test connector under the dash. Count the flashes of the check engine light with the ignition on. One flash pause then 2 flashes is a code 12 and means the system is working. Each code wil repeat 3 times, then the next one will show.