P0128
DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)TECHNICAL DESCRIPTION
- The ECM checks the time for the cooling water temperature to reach the judgement temperature.
DESCRIPTIONS OF MONITOR METHODS
Engine coolant temperature does not reach 77 °C (171 °F) within specified period after cold start.
MONITOR EXECUTION
Once per driving cycle
TECHNICAL DESCRIPTION
- The ECM checks the time for the cooling water temperature to reach the judgement temperature.
DESCRIPTIONS OF MONITOR METHODS
Engine coolant temperature does not reach 77 °C (171 °F) within specified period after cold start.
MONITOR EXECUTION
Once per driving cycle
DTC SET CONDITIONS
Logic Flow Chart:
Check Conditions
- Engine coolant temperature is between -10 °C (14 °F) and 60 °C (140 °F) when the engine is started.
- Intake air temperature is -10 °C (14 °F) or higher.
- The intake air temperature when the engine is started - intake air temperature is 5 °C (9 °F) or less.
- The total time of the mass airflow sensor output whose state is over 14 g/sec within 440 seconds.
Judgement Criteria
- The time for the engine coolant temperature to rise to 77 °C (171 °F) takes longer than approximately 10 to 38 minutes.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 10. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- The engine cooling system is faulty.
- ECM failed.
DIAGNOSIS
STEP 1. Check the cooling system.
Refer to Engine Cooling Diagnosis. Testing and Inspection
Q: Is the cooling system normal?
YES : Replace the ECM. When the ECM is replaced, register the ID code. Then go to Step 2.
NO : Repair it. Then go to Step 2.
STEP 2. Test the OBD-II drive cycle.
1. Carry out test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 10. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0128 set?
YES : Retry the troubleshooting.
NO : The inspection is complete.