'check engine' came on today.

I've done the stomp test before on this car and it gave me codes, but now when i do it it flashes off for half a second then goes back on and just stays on.

Suspected bad fuel pressure regulator, I've been getting lousy mileage lately - there is a new one on the way, but wouldn't it at least give me a code? Otherwise I don't notice anything and it idles fine. Hope it's not the cat... Ideas?