IS the light always on? The left lower lever on the steering column will turn off the visual display on the bottom of the instruments, but not the light itself. There are several reasons for the light to go on, and I'm not competent to give the complete rundown, but Alan Moore in Phoenix is (do a search for Alan on Renlist 928 Forum). Others may be as well. Alan's subtitle on Rennlist 928 Forum is 'electron wrangler.
If the light comes on when the car is started, and later goes off after a few minutes of running/driving, then it may be the controller itself. I believe there is one or more capacitors in the unit which hold charge but as they age lose the ability to hold a full charge. When they reach full charge again, the light goes off. I've had that happen on two different GTS's, where the light would not come on if the engine was started within a few hours after being turned off, but if the car was not started again for several days, it repeated the 'on, for a minute or so, then off' action.
Gary
