its a long story but let me explain to you,when I bought my car airbag light was on thats why I went to the porsche repair shop.they try to erase the foult code but they coudnt, and they told me that the control unit and the left sensor must be change and the cost was 4000euro so I bought a used but working unit and sensor from ebay and changed it .then went to the same shop they pluged the tester and erased the foult code but the light was still on but the tester doesnt give any foult code after a few minutes light was off .I tought everthing was ok.after a few day suddenly light came on again .cleared the code again this time it was( unit and the light) foult code. 2 weeks later the light came on again. what I MUST DO ? please help or any idea about this situation,

 

I have had a similar problem and it is quite common. The fault code I suspect was to do with resistence and basically it means the connections to the sensors need cleaning. I haven't got my car here at the moment so I cannot take pictures for you but maybe someone else on here can.

DOUBLE CHECK THIS BEFORE YOU START!!! but I think you need to disconnect the battery for at least 30 mins before you disconnect the sensor connections. Clean them up and reconnect them. THIS WILL NOT CLEAR THE WARNING LIGHT. You need to take the car back to someone who has the diagnostics computer and have the warning reset as it will not reset itself.