Home >> Lexus >> 2009 >> IS 250 RWD, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> Testing & Diagnosis >> Engine Control System (DTCS P0010 - P0368) >> SFI System >> DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) >> Typical Malfunction Thresholds