Your engine is taking too long to reach its normal operating temperature. The thermostat, which controls coolant flow, is likely stuck open, allowing coolant to circulate too freely and preventing the engine from warming up efficiently.
Find certified mechanics near you who can diagnose and repair P0128.
For informational purposes only. Diagnostic trouble codes are starting points for diagnosis, not definitive answers. Always consult a certified mechanic for proper diagnosis and repair. Estimated costs vary by vehicle, location, and shop rates.