One problem related to brake light switch has been reported for the 2003 Cadillac CTS. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Cadillac CTS based on all problems reported for the 2003 CTS.
2003 Cadillac safety issues: premature and rampant failure of the ebcm - electronic brake control module. It is widely known these modules fail and cannot be rebuilt. Dealer cost is over $500 with most dealers charging more than $750. Premature and rampant failure of the rear center brake light. Gm even admitted failure of the neon lights used for this application and quickly switched to a reliable light media. Replacements range from $250 used (if you can find one that works) to $500 retail at gm. Both of these units are known high failure items and both cost a fortune through your local gm dealer.