Paul:
A loose connector won't cause it. The circuit looks for a ground, so you're looking for one of the wires to be cut into, just nicked a little, causing a path to ground. You can yank all the sensor wires out and that light will never come on (normally).
Look in the area of the anti-rattle clips between the pads, or the wire can actually just be rubbing against a rim, which is tough to catch if you don't know "it can do that", because you pull off the offending wheel, and "what a ya know", it's not rubbing ANYWHERE now!
Gilly