how to read Chevrolet Astro fault codes

Hello a greeting everyone ....

I hope someone can help me ...
I have a chevrolet astro 1986 with Obd 1 and I know that I can bridge two pins of the diagnostic connector to read the codes on the board with the focus engine focus ... but I do not know between which one and which pin I have to give up the bridge ...
I hope to help me and if you could get a list of erros codes ...
Thank you

You must bridge the Terminal A and B with a clip, you open the Ignition SW and the light a thousand will begin to flash the slower flashes are the tens and the fastest the units These codes are of 2 digits usually the one that always gives is the 12 that means that the engine is not turning the diagnosis connector must have a guide for the diagnostic connector and should be a square