I've been getting this warning almost every time I get in my car (997TT) for the past month. Sometimes it comes on right away, other times it comes on after 20 miles or so. I've had the battery tested and it's fine. My local dealer couldn't figure out what it was on my first visit so the car is going back in next week. Has anyone else had this warning? The CEL's are driving me nuts.

 

Does the car idle a little low on initial fire-off?(lower than normal initially and then idle-up? If car idles low will not excite alernator diodes until rpms come up. Could be exciter diode issues with the alternator itself. Perhaps a belt tension prob. allowing a small amount of slip on start up. Do you ever hear any noise at start up or feel/hear anything out of the ordinary? Will ck TSBs.

 

It actually idles fine and isn't showing any other problem symptoms (other than the warning light).

 

alternator shot. just had the same thing on my car. no biggie, warranty and done.

 

Mine will do that whenever it rains, because the belt slips. In your case it does it all the time, either you have a loose belt or a bad alternator.

 

Thanks for the feedback, guys. Hopefully Porsche will replace my alternator on warranty without any arguments.