service engine soon on 1999 Cadillac Seville STS

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
why does my cadillac only turn on when service engine soon light is on..?
(1) Answer
I'm not sure I understand this. The service engine soon light is the check engine light. You can read more about it here:

It means that there is a problem with your car that could definitely be serious enough to affect starting.