2004 Cadillac CTS Owner's Manual - Page 309

When to Inspect the Engine Air Cleaner/Filter Inspect the air cleaner/filter at every oil change and replace it at the first oil change after 25,000 miles (40 000 km) {CAUTION: Operating the engine with the air cleaner/filter off can cause you or others to be burned. The air cleaner not only cleans the air, it helps to stop flame if the engine backfires. If it is not there and the engine backfires, you could be burned. Do not drive with it off, and be careful working on the engine with the air cleaner/filter off. How to Inspect the Engine Air Cleaner/Filter To inspect the air cleaner/filter remove the filter from the vehicle and lightly shake the filter to release loose dust and dirt. If the filter remains caked with dirt, a new filter is required. To inspect or replace the filter, do the following: 1. Remove the two screws located on the sides of the cover. 2. Lift the cover off. 3. Pull out the old engine air cleaner/filter. 4. Install a new engine air cleaner/filter, if needed. See Normal Maintenance Replacement Parts on page 6-15 for the correct part number for the filter. 5. Reinstall the cover by reversing Steps 1 and 2. Notice: If the air cleaner/filter is off, a backfire can cause a damaging engine fire. And, dirt can easily get into your engine, which will damage it. Always have the air cleaner/filter in place when you are driving. 5-23