Why is heater not working on a 2002 envoy XL?

If the heater in a 2002 Envoy XL is not working, it could be due to several reasons. Common issues include low coolant levels, a malfunctioning thermostat, or a faulty heater core. Additionally, check for a clogged heater core or issues with the heater control valve. Inspecting these components can help identify the problem and restore heating functionality.