Which issue could lead to low air flow through instrument panel duct outlets?

Low airflow through the instrument panel duct outlets can occur due to a variety of issues related to the heating and air conditioning system, including those listed in the options.

A faulty blower motor would directly impact the system's ability to move air through the ducts. If the blower motor isn’t functioning properly, it may not be able to provide adequate airflow, regardless of the other functioning components, leading to low airflow at the outlets.

A clogged passenger compartment air filter can hinder airflow as well. When the air filter is blocked with dirt and debris, it restricts the amount of air that can pass through it, resulting in reduced airflow through the duct system and, consequently, at the instrument panel outlets.

Additionally, a stuck mode door, which controls the direction of airflow within the HVAC system, can prevent air from reaching the desired outlets. If the mode door is unable to open or close correctly due to mechanical failure, the airflow may be diverted away from the instrument panel ducts, resulting in low airflow.

Since all these components can individually contribute to low airflow issues in the same way, choosing "all of the above" effectively encompasses all the possible causes, making it the comprehensive answer to the question.