The GMC Sierra line includes a number of different pickup truck models built for both hard work on the farm and a night out on the city. One of their newest models, the Sierra Hybrid, even features hybrid engine technology for better fuel mileage. Although it's no longer standard, from 1999 to 2006, the Sierra featured an in-cabin air filter to help clean out allergens and pollutants. If your heating or air conditioning on one of these models isn't blowing as hard as it used to, one thing you can try is replacing your cabin air filter.
Park your Sierra on a flat and level spot. Place an old blanket or dropcloth on the ground beside the passenger side door. Open the passenger side door. You'll be doing a lot of work down low, so get comfortable.
Take the flashlight and look for the plastic panel that is located underneath the glove box. On most Sierra models, this is held in place with four screws. Use the screwdriver to remove the screws. Take the panel and screws and set them aside.
Locate the hinged door to the air cabin filter located beneath the panel you removed. Remove the screw holding the door in place and allow the door to swing open downwards.
Remove the old air filter by pulling downwards. Replace the new air filter in the slot, making sure that the arrows on the filter are pointing towards the cabin.
Close the cabin air filter door and secure in place with the screw.
Replace the access panel. Secure with the screws.
