How do you read trouble codes 1991 Mitsubishi mighty max pickup?

Under the dash, behind where the fuse box is, is a large connector with 3 male pins inside.. there are two in opposite corners and a third next to one of the previous two... what you want is the two in the corners ( one is to the computer, the other is a ground).. Get a 12volt LED with built in resistor and (mine has 2 insulated wires and is made to mount in a panel) at Radio Shack . Also get a pack of small alligator clips.. crimp a clip on each wire , then hook to the two aforementioned pins in the connector with the key off... Turn on the key... The LED will flash a code to you- a long flash= "10".. a short flash= "1"..So, two longs followed by 3 shorts would be 10+10+1+1+1= 23 (example) then look up fault code 23 ( possibly even call the dealer, autozone,etc...)