Buick 2009 Lucerne Owner's Manual page 173

To access the passenger compartment air filter,
do the following:
1. Press the tabs back and left to remove the cover.
2. Insert a tool behind the push pin located on the
inboard side of the air filter compartment to
carefully pry the pin out.
3. To remove the air filter, insert a tool between the
air filter and the compartment wall on the outboard
side of the vehicle. Then, push in to flatten the
pin holding the air filter in place. Gently remove the
air filter and any loose debris that may be inside
the air filter compartment.
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