What does the cadillac catera sport indicator light do?

There's a website that has all this information about all this and manuals everything totally free there are many actually but I personally like few reliable-store for eg. .. let me know if u need help
thanks

Sport Mode Indicator Lamp and Automatic Transmission Warning Lamp (STL)
The sport mode indicator lamp illuminates when the vehicle has been put into the sport mode by pressing the "S" button on the gear selector. When this lamp is illuminated the vehicle will have slightly firmer shifts and increased performance for part and full throttle situations.
This lamp will also flash when there may be a problem with the automatic transmission. The transmission control module (TCM) performs a continual self diagnosis of certain control functions. The lamp will flash only when an error is detected. The TCM will store in memory a current and/or history trouble code when a problem is detected. I'd have it checked out !

I wouldnt bank on this but it sounds like a shift syliniod

You could have a problem with either the headlamp or dash dimmer switch but test all the fuses first.

WHAT problem would that be?

I have a indicator lamp with an exclamation mark which is tied to a Check Engine lamp. And upon purchase of car, there wasn't a manual. I have NO clue what that " ! " lamp means, but it's affecting the gear box of my automatic transmission.

The car performs a vacuum check at start up. If there is a leak in the tank, lines etc. the fuel cap will come on.

This and other details can find it in 2001 Cadillac Catera - Owners Manual.

Hope this helped (remember comment and rated this).

http://www.fixya.com/cars/p698563-cadillac_2001_catera/manual-24492

You should find it in here. Not much difference between a 99 and an 01.

in the owners manual the sport light does a couple things depending on the make up of your catera.
start there, i don't have the owners manual with me or i would review.