Question

vehicle: 2015 VW beetle 1.8 engine:  I change the battery and the electronic control in the steering wheel (control for time setting, phone answering button, horn, etc) failed. what are the possible cause, how to diagnose and fix

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Answers

If the entire control doesn't work, its possible you blew a fuse and just need to replace that; check the fuse panel for a dead one.  It could also be that the button itself failed and needs to be replaced.  What exactly does this controller look like?  That'll make it easier to diagnose.