Where is the diagnostic connector?

You have that pesky engine warning light. You checked the manual and can't find the test plug.  So where is it?

Trying to find the diagnostic connector (test plug) on your 1991 Ford Ranger is challenging if you have never seen it. It is at the end of the Power Distribution Box on the inner fender firewall on the passenger side of the engine compartment. If it has not been pulled from its cover (a molded socket) it is harder to find. 

Below is a picture of what you are looking for (not from my Ranger).  Your power box maybe different but the diagnostic cover (socket) will be marked the same.  This "cover" is usually covered with dirt and grease, wipe it off and you can see the wording. There is also the gray "pigtail" beside the connector.  You can see it in the photo.

The connector just slides in this holder from the bottom.  Just pull it out from below and there you go.

Now what? Using your connector, you can now get your codes via the flashing light. Below is one way of doing it, your service manual may show another, or you can use an older plug-in style code reader.

For me, I have decided to keep my connector out of the holder, less I forget where the damn thing is.