Hi Mokew,
Make sure that there is not anything on the dashboard covering the sensor. I think that the Cadillac also has two knobs for the sentinel? One for On and one for the delay? Just make sure that it did not get accidentally turned off. Those were the most common problems I saw on Buicks, some papers on the dash, a new dash cover or the switch was bumped to off. Forgot to ask, lights staying on or not coming on at all? If everything looks Ok then it might be time to take it into the shop or pick up a shop manual and do some reading on how to repair it.
Good Luck to All! :^)
PLAN the TRADE and TRADE the PLAN!