DTC P0128 Coolant Thermostat (Engine Coolant Temperature Below Thermostat Regulating Temperature): Notes
WARNING: This page is about a different variant/trim than selected.
DTC detecting condition:
Detected when two consecutive driving cycles with fault occur.
Trouble symptom:
- Thermostat remains open.
- Coolant temperature rises slowly.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Clear Memory Mode>OPERATION
. and Inspection Mode Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Inspection Mode>PROCEDURE
.
- CHECK FOR ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?
- Yes: Check the appropriate DTC using the "List of Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>List of Diagnostic Trouble Code (DTC) .
- No: Go to 2.
- CHECK ENGINE COOLANT.
Is the engine coolant amount normal?
- Yes: Go to 3.
- No: Refill the engine coolant. Ref. to COOLING(H4DO)>Engine Coolant .
- CHECK RADIATOR FAN.
- Start the engine.
- Check the operation of the radiator fan while keeping idling (acceleration OFF) for approx. 3 minutes.
Does the radiator fan continuously rotate for 3 minutes or more during idling?
- Yes: Repair radiator fan circuit. Ref. to COOLING(H4DO)>Radiator Main Fan and Fan Motor and Ref. to COOLING(H4DO)>Radiator Sub Fan and Fan Motor .
- No: Go to 4.
- CHECK ENGINE COOLANT TEMPERATURE SENSOR.
Check the engine coolant temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>Engine Coolant Temperature Sensor>INSPECTION .
Does the radiator fan continuously rotate for 3 minutes or more during idling?
- Yes: Replace the thermostat. Ref. to COOLING(H4DO)>Thermostat .
- No: Replace the engine coolant temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>Engine Coolant Temperature Sensor .