I recently bought a Audi A4 2006 Cab
The car only came with 1 Key, that key Locks/Unlocks From Barrel And Starts the car. remote wont work.

I got in touch with the previous owner and he had a key the original that he used for 2 years, which i got of him, this key locks/unlocks the car on the remote fob,
Starts the car for a few seconds only, by this i mean the word ''safe'' is displayed above the trip meter computer and cuts out. lasts about 5 seconds

Anyone know why this would/could happen?

i dont want to play around with it too much as iv read on Google and other sites that this can mess up both keys, 1st key still working.

please help.