GM 1983-95 vehicles OBD1 codes self-retrieval
As the name implies, you can get the codes for GM cars or trucks yourself if the model of your vehicle is made before 1995, this means as soon as you see “check engine light” in your dash, you can get the code in minutes if you want.
Shown on the left is a picture of the connector where you get the GM OBD1 code.
When you find the adapter connector, use a jumper wire (see red wire above) and connect terminals A and B. Next turn your key on but don't start. Watch your check engine flash the code/s.
EXAMPLE: CODE 12: one long flash and two short flashesCODE 13: one long flash and 3 short flashes.
Note: code 12 is usually the first code you get and just ignore it.Watch the code after code 12, that's what you need.