on G2's, the Brake light (same light on the dash that corresponds with the e-brake) will come on if the brake fluid is low. I can personally vouch for checking the fluid. If you look on the master cylinder, the cap that goes over the fluid reservoir ("screws on" with about a 1/4 turn, and is air tight) will have two wires coming from it. they sense how much fluid is in the reservoir.
IF you check your sensors on the parking brake AND the fluid, and they both come out fine, go to a junkyard and get a new "cap" for the master cylinder. its easier and cheaper than fixing the sensor. depending on what junkyard you go to, you can just snipe it right off and not have to pay for it. its a VERY easy fix, and will literally take a minute, just unplug the wires, plug up the new wires, put cap on, done.
this much, I could be mistaken on, but i THIIIINK that the cap is the same on pretty much all Integras. Might even be the same as any civic with a similar brake setup (Si's etc.) as the Integra.
hope that helps.