Few years ago I bought a XSi then a year later I bought a 6, tried to sell the XSi for a bit, couldn't so its been in garage since. Have sold the 6 now and trying to get the XSi going again. The engine turns over but thats about it.

Im just wondering if the immobiliser is the problem and how I would tell? As I remember swapping the key cases around and its a possibility that the transponder chip in this key fob is for the 6 I sold. This is the only key I have for it.

Any help would be appreciated, thanks.