Have you got a second key for your car that does not work? Have you replaced the batteries and it still does not work?
Does the button feel like nothing happens once you press it?

I had this issue myself and was able to get it working again. It required a bit of soldering but however it worked like a charm.

If you would rather not attempt this yourself for a small fee I would be more than happy to do it for you.

I ordered this button which is the replacement part: https://cpc.farnell.com/multicomp/tm...-ddd7-00001003

Removed existing button which had exploded, grease all over the board and soldered the new one on.

Replaced the battery, reprogrammed to the key and it works!

Subaru said about £300+ for a new key and I managed to fix mine for about a tenner.

 

Nice info, and nice to offer a service. All my Impreza'a have the sigma alarm which over rides that button.

 

That key, with one button, is the key that arrived, AFAIK, with MY03 (at least it did with the forester) that has the subaru pcb removed and the one button sigma operating pcb fitted instead plus a new cover.
Prior to that you have the original two button keys (with battery removed) plus sigma fob/s.