P0128
Coolant Temp Below Thermostat Regulating Temperature
OBD-II
Cooling
What it means
The engine is not reaching normal operating temperature — almost always a thermostat stuck open. Cheap to fix, and it hurts fuel economy and heater output until you do.
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Check your car freeRelated codes
P0115
Engine Coolant Temperature Circuit
CoolingMedium
P0116
Engine Coolant Temperature Circuit Range/Performance
CoolingMedium
P0117
Engine Coolant Temperature Circuit Low
CoolingMedium
P0118
Engine Coolant Temperature Circuit High
CoolingMedium
P0119
Engine Coolant Temperature Circuit Intermittent
CoolingMedium
P0125
Insufficient Coolant Temperature for Closed Loop Fuel Control
CoolingLow
P0126
Insufficient Coolant Temperature for Stable Operation
CoolingLow
P0217
Engine Coolant Over Temperature Condition
CoolingCritical
General reference only — what a code means can vary by make and model. Confirm with a qualified technician.