Originally Posted by Fabrik8

Most Japanese cars have much better connectors that domestic cars. Many of these connectors have a secondary lock plate on them, which is snapped into place after all the pins are inserted into the connector shell. So what you most likely need to do is figure out how to release the secondary lock plate, it will usually raise right up or hinge out. There are a bunch of different styles of lock plates, and I can't see the connector you're working on. Anyway, if the secondary lock is still in place, the pins aren't going anywhere even if you release the primary lock from the front (like you're trying to do now).. There is usually one secondary lock per side if it's a two row connector. If it's a 3 row connector there is usually a plate that snaps in from the back, and secures all 3 rows at once. It's usually a different color for 3 row connectors because it's molded as a seperate piece.

Post a high res pic of the connector and I'll tell you what brand it is and how to release the lock.

I'm going to take a random guess and say you're working on a Nissan. Honda locks are easy to figure out just by looking at the plug, Nissans not so much. I'll bet it's one of the single piece ECU connectors with the retaining screw right in the middle of the plug. I'll have to have a pic, I don't remember what type of lock they have.