If you hear clicking sounds after your turn off the engine near the bottom of the driver side door (assuming your X is LHD) the actuator gear in the transfer case is stripped. If you don't hear the clicking when you shut off the engine, it's something else. Most likely a wheel sensor. In addition to the wheel sensor, get a new connector case for the wiring harness because when you go to remove the wheel sensor connector from the car wiring harness the plastic connector will crumble.

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2006 Infiniti G35
2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD
Lotus Europa 1970 Destroyed by fire
Lotus Europa 1970 S2 Renault Powered
Lotus Type 52 1970 Twincam Webers Powered
PORSCHE 911 Targa 1982 The Garage Queen
Audi Avant donated to Kars for Kids
BMW 525IT Sold
Audi 4000CS Quattro Sold
Jensen Healey Lotus Powered Sold
Opel 1900 Sold
Triumph Spitfire 1971 Sold
Triumph Spitfire 1968 Sold
Plymouth "Cuda" 340 Six pack SOLD