Chevrolet Volt cabin heat not working on electric mode, heater service message displayed on Chevrolet Volt

Some Chevrolet Volt owners report experiencing issues with cabin heat not working in electric mode, often accompanied by a heater service message. Common causes of this problem may include a clogged filter that affects system efficiency, or issues with the electric coolant pump, which may produce unusual noises when failing. Additionally, coolant leaks from the radiator or inadequate isolation resistance in the high voltage system can further impact heating performance. To diagnose the issue, some owners find it helpful to check for heat in both electric and gas modes, and inspect components such as the aux coolant pump and coolant bypass valve. If the heater does not warm up as expected, consulting a Volt adviser for further guidance is recommended. Common failure points include heater core leaks and malfunctioning pumps or valves, which can prevent proper heat circulation under electric mode while still functioning in gas mode.