Yep, they a right **** to sort out!
Engine at idle.
[44-Steering Assist]
Rotate steering wheel 90deg left then center, 90deg right then center so steering wheel is level, front wheels pointed straight ahead.
[Security Access - 16]
Enter 19249
[Basic Settings - 04]
In Basic Settings, pick [MAS00815] Steering angle sensor
[Go!]
Rotate steering wheel all the way to the left, hold firmly against end stop for 5 seconds.
Rotate steering wheel all the way to the right, hold firmly against end stop for 5 seconds.
Center steering wheel, front wheel straight ahead.
Note: our testing of this would still be "Running", never got a message of "Finished Correctly"
[Stop]
Now a bunch of error messages and warnings will appear on the cluster, what messages you get can vary based on how the vehicles is equipped.
[Done, Go Back]
Rotate steering wheel all the way to the left, hold firmly against end stop for 5 seconds.
Rotate steering wheel all the way to the right, hold firmly against end stop for 5 seconds.
Center steering wheel, front wheel straight ahead.
Now most warning messaged in instrument cluster should be removed.
[Close Controller, Go Back - 06]
Cycle the ignition off for 10 seconds.
Several other control modules will flag DTCs, "Databus" type codes that can now be cleared out.