The spark plugs in your 2003 Cadillac CTS are long-life plugs that use an ignition coil instead of spark plug wires to deliver the spark necessary to ignite the fuel in the engine. The CTS spark plugs are designed to last 100,000 miles, as opposed to the typical life of 30,000 miles for most other spark plugs. When the plugs do need to be changed, replacement plugs can be purchased from most auto parts stores.
Open the hood of the CTS and unbolt the engine cover bolts located around the outside of the engine cover; remove the engine cover.
Unbolt the intake manifold bracket bolts located on the left side of the engine, then remove the intake manifold mounting bolts.
Unscrew the hose clamp that holds the air intake tube to the throttle body; slide the hose clamp out of the way and pull the intake tube off the throttle body. Push it to the side for a moment--you'll need to do this to move the intake manifold.
Pull the intake manifold away from the engine and move it out of the way, so that you can access the #2 plug on the engine.
Unbolt the retaining bolts on the spark plug coils for all of the plugs, then pull the coils out of the engine.
Unbolt the spark plugs, using a spark plug socket and socket wrench. You will need a socket extension, since the spark plugs are located inside the plug well and are not easily accessed by using just the spark plug socket.
Pull the old spark plugs out with the socket and insert the new plugs. Thread and tighten the new spark plugs. Installation is the reverse of the removal process.
