Volvo All Engines (2017 Emissions) Fault Code: P012800 PID: EMS Coolant Thermostat (Cooolant Below Thermostat Regulating Temperature)

Volvo All Engines (2017 Emissions) Fault Code: P012800 PID: EMS Coolant Thermostat (Cooolant Below Thermostat Regulating Temperature)

A fully functioning coolant thermostat is closed at room temperature
If the thermostat sticks open coolant will pass through and the engine will never reach operating temperature
If the thermostat is stuck in open position the engine will not reach operating temperature
If the thermostat is stuck in closed position the engine will not be cooled

Conditions for diagnostic trouble code (DTC):
1) The component is stuck in opened position

Observable symptoms
1) Engine does not reach normal operating temperature

Probable cause
1) The thermostat may have seized in open position if the engine has been warmed up too slowly

Detailed information
1) By comparing calculated and measured coolant temperature on a hot engine, one can determine if engine warm-up occurred sufficiently fast