It is one wire that goes around the entire car and if it is broken, the light will go on. There is some logic in the DME that decides when to turn it on or off but that is 99.9% irrelevant to your problem as it is only used to ensure the light doesn't flicker or go on and off a lot when the wire is first broken and the DME is not prone to error.
You can diagnose where the break in the wire is located by using a continuity tester and testing the continuity of each sensor and also the continuity between the sensor on one wheel to the continuity of another. Chances are you have a bad sensor. I've seen that before, even on relatively new sensors.
You can actually test the continuity of the sensors with the car sitting on the ground and the wheels on the car. You reach around or through the wheel, unplug the sensor, and stick the continuity tester on the two plugs.
The only other remaining possibility is that the sensor is not making good contact with the plug on the car. That would become evident by wiggling each sensor plug.
I have used a trick where I put a digital camera on the sensor light while I wiggle each plug and then bridge the connector. I say out loud "left rear wiggle", "right rear bridge", etc. Then after I've wiggled them all, I view the video and it tells me exactly where the problem is.