My wife's Cayenne had new brakes installed about a year ago, probably less than 3k miles since. Now, after driving about 10 miles when braking the sensor alert pops up on screen. Tire/brake shop said nothing obvious when checked, they cleared warning but it has come back.

 

Sensor activates by the circuit being disrupted. When the tip of the sensor hits the rotor and grinds through the circuit is opened and continuity is lost. There is a plug for the sensor to the body harness behind each wheel. You can check the sensors for continuity and check that the connectors are making full contact.

I don't run the sensors on mine. I have taken the sensor plug and twisted the two wires together to complete the circuit.

 

anyway to tell which wheel sensor is acting up?

 

Not really. You will have to physicaly inspect each one.