A sensor in the emissions system has gone low.

Try
http://www.scoobymods.com/forums/showthread.php?s=fec17e12624b0b14a69bbc2569
47adfa&p=14318#post14318
Same problem, looks like you've gotta jack your car up and f.ck around with
some wiring.

Basically, as most subarus are built the same at the factory, then tuned,
detuned, and extra gear put on in the country they'll be sold - ie your
emissions gear - it's probably a hack job with the wiring.

As the bloke above has done, if the solder joint is too corroded to fix,
then use a pinch / splice connector. Just make sure you crush the metal tab
in properly.

Also, reinforce it from the weather. Some liquid electrical tape should do
it, from a good electrical store.

-mark