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Home >> Subaru >> 2015 >> WRX Limited, Automatic CVT Trans >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 7 (Engine Controls (Diagnostics) (H4DOTC) (STI)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0128 Coolant Thermostat (Engine Coolant Temperature Below Thermostat Regulating Temperature) >> Trouble Symptom

DTC P0128 Coolant Thermostat (Engine Coolant Temperature Below Thermostat Regulating Temperature): Trouble Symptom

WARNING: This page is about a different variant/trim than selected.

Thermostat remains open.

CAUTION: After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to OPERATION , Clear Memory Mode.>, and Inspection Mode <Ref. to PROCEDURE , Inspection Mode.>.
DIAGNOSTIC PROCEDURE

Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY.  Is any other DTC displayed? Check the appropriate DTC using the "List of Diagnostic Trouble Code (DTC)". <Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) .> Go to step 2. 
2 CHECK ENGINE COOLANT.  Is the engine coolant amount normal? Go to step . Refill the engine coolant. <Ref. to ENGINE COOLANT .>
3 CHECK RADIATOR FAN. 
  1. Start the engine.
  2. Check the radiator fan operation.
Does the radiator fan continuously rotate for 3 minutes or more during idling? Repair radiator fan circuit. <Ref. to RADIATOR MAIN FAN AND FAN MOTOR .> <Ref. to RADIATOR SUB FAN AND FAN MOTOR .> Replace the thermostat. <Ref. to THERMOSTAT .>