Steering wheel no electrics
 

I have just bought a second hand Cayenne 2005 S.

The steering wheel controls do not work at all, no lights or tiptronic and when I start up I get an airbag warning.

I have checked all fuses in the drivers side and the passengers side - all are working that are in place (not sure if one is missing).

Does anyone have any idea what to check or access to a diagram so I can start tracing the fault to see where to look.

Thanks