OK, I just went under my car and pulled it apart. The red tab is pushed in from the left towards the right. The Tab or bottom part of the "U" which is bigger than the sides of the "U" is pushed down so the top part lifts over 2 little notches that you can't see until the connector comes apart. If the bottom part of the tab is broken off by lifting instead of pushing, you might want to stick a small screwdriver into the space between the two halves to lift the upper part of the connector over the tabs. while lifting the upper part, pull down on the bottom part of the connector and hopefully it will come apart.
That's what I just had to do because my tab is broken off
which I must have done the last time I messed around with it.
OK, lousy job of messing around with a photo, but this white outline shows where the black tab on the connector is. Push it down so the top part of that tab lifts over the 2 small notches that are holding the connector together.
