Replacing steering angle sensor is very easy, only 15 minutes job. Just buy the part from 3rd party parts dealer and diy. Take a look at below link:

BMW TIS - 32 31 082 Removing and installing/replacing steering angle sensor

Remember you must encode the sensor and adjust the sensor after replacement with BMW TIS.

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--2004 E53 X5 4.8is - ECE version; right hand drive; Located in Hong Kong; ext. black sapphire metallic; int. leather black; adaptive dynamic bi-xenon headlights; 16:9 onboard monitor w/o navigation; 20" genuine BMW Y-spoke 214 wheels with Bridgestone Dueler H/P Sport tires; Int. rear view mirror w/ compass.