What does the MG ZS engine P012800 mean?

[Evie]

The MG ZS engine P012800 indicates that the engine coolant temperature (ECT) is below the thermostat regulation temperature. Possible cause: The vehicle's thermostat is equipped with a spherical valve to control the volumetric flow rate of the coolant. The fault code P012800 may be caused by a stuck spherical valve. Thermostat working principle: The thermostat automatically adjusts the amount of water entering the radiator based on the coolant temperature, changing the water circulation range to regulate the cooling capacity and ensure the engine operates within the appropriate temperature range. The thermostat must maintain good technical condition; otherwise, it will seriously affect the normal operation of the engine. Too late and too early: If the thermostat's main valve opens too late, it will cause the engine to overheat; if the main valve opens too early, it will prolong the engine warm-up time, resulting in the engine temperature being too low.