On my 1999 integra there is a plastic container with some hoses going
into it that sits under the inside corner of the battery, about six
inches down. From (over)filling the battery, acid had dripped down and
eaten a hole in the top of the plastic container. That hole was
causing the check engine light to come on.
I don't know to this day what the container is for. I cut out a
little triangle of stiff plastic, gobbed some adhesive on there and
covered up the hole nice and air-tight. Let it dry for a day, unhooked
the battery to re-set the light and fired it back up. That was two
weeks ago and the CE light has not come back on since.