Pontiac G5 coolant temperature warning and fluctuating temperature issue on Pontiac G5

Some Pontiac G5 owners report experiencing coolant temperature warnings and fluctuating temperature gauge readings. These issues may be linked to the P0128 OBD II trouble code, which indicates that the engine coolant has not reached the required operating temperature in a timely manner. Owners have noted that fluctuating readings can stem from problems such as a faulty thermostat, insufficient coolant levels, air in the cooling system, or defective coolant temperature sensors. Additionally, some report that a temperature reading of 120 degrees Celsius could suggest an air bubble in the system, which might require a specific filling procedure to resolve. To address these concerns, it is advisable for owners to check coolant levels, inspect the thermostat, ensure there are no air pockets in the cooling system, and consider testing or replacing the coolant temperature sensor. Prompt attention to these issues can help prevent further complications with the Pontiac G5's cooling system.