2004 Cadillac DTS 100,000 miile tuneup.

At 100k miles, you can replace the spark plugs, the coils are not necessarily needed. The fuel and air filters can be considered. You may also consider cleaning the throttle plate and idle air control valve pintle and passage. Depending on what your maintenance practices have been, running some cleaner through the injectors, performing some fluid services, like transmission and brake fluid exchanges, can also be part of it. There is a ventilation filter that is easily accessed for replacement, as well.