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Home >> Ford >> 2009 >> Flex Limited, FWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Powertrain DTC Charts & Descriptions (Except Diesel & Hybrid) >> DTC Diagnosis >> DTC P0128: - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

DTC P0128: - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

DTC P0128: - COOLANT THERMOSTAT (COOLANT TEMPERATURE BELOW THERMOSTAT REGULATING TEMPERATURE)

Description:  Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.
Possible Causes: 
  • Insufficient warm up time
  • Low engine coolant level
  • Leaking or stuck open thermostat
  • Damaged ECT sensor
  • Damaged CHT sensor
Diagnostic Aids:  Refer to THERMOSTAT MONITOR for system information.
Application  Key On Engine Off  Key On Engine Running  Continuous Memory 
Explorer 4.0L,
Explorer Sport
Trac 4.0L,
Fusion 3.0L,
Milan 3.0L,
Mountaineer 4.0L,
Mustang 4.0L,
Ranger 4.0L
- - GO to Pinpoint Test DX .
All others - - GO to Pinpoint Test DL .