You can downlo0ad the manuals from the Miele website. It does have this code in.
F17 - Catalyser temperature sensor is defective.
I think the cat. is used to burn off odours in the oven to reduce the cooking smell in the kitchen. If the temperature sensor is faulty the cat won't be turned on so you may notice more delicious smells than you're used to!
James, May 2011