Thinking of changing them
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2003 Cadillac DeVille DTS Question: Where are the spark plugs located on Cadillac DTS 2003
Answer #1big01_dram July 11, 2011, 13:09Journeyman
They should be under the engine cover. I found this which should help you. http://wiki.answers.com/Q/How_to_replace_spark_plugs_on_2... It may not look familiar because they used a coilover coil pack on your car. Basically instead of a central coil pack with plug wires running to the plugs, there is a plastic thing with a short boot on the bottom. you probably wont even see the boot until you remove the coilover. This pic should give you a better idea of the assembly.
it is easy to do the front but a tight squeeze to get to the back. Good luck.