P0128

DTC P0128 THERMOSTAT FUNCTION





On Board Diagnosis Logic
Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough.
This is due to a leakage in the seal or the thermostat being stuck open.









DTC Confirmation Procedure

NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.
1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
TESTING CONDITION:
- For best results, perform at ambient temperature of �10�C (14�F) or higher.
- For best results, perform at engine coolant temperature of �10�C (14�F) to 56�C (133�F).
- Before performing the following procedure, do not add fuel.

WITH CONSULT-III
1. Turn A/C switch OFF.
2. Turn blower fan switch OFF.
3. Turn ignition switch ON.
4. Select "COOLAN TEMP/S" in "DATA MONITOR" mode with CONSULT-III.
5. Check that the "COOLAN TEMP/S" is above 56�C (133�F). If it is below 56�C (133�F), go to next step.
If it is above 56�C (133�F), cool down the engine to less than 56�C (133�F). Then go to next steps.
6. Start engine and drive vehicle for 10 consecutive minutes under the following conditions.






7. Check 1st trip DTC.
8. If 1st trip DTC is detected, go to P0128.

WITH GST
1. Follow the procedure "WITH CONSULT-III" above.




Diagnosis Procedure
1.CHECK ENGINE COOLANT TEMPERATURE SENSOR
P0128.
OK or NG
OK - GO TO 2.
NG - Replace engine coolant temperature sensor.
2.CHECK THERMOSTAT
Component.
OK or NG
OK - INSPECTION END
NG - Replace thermostat.




Component Inspection

ENGINE COOLANT TEMPERATURE SENSOR





1. Check resistance between engine coolant temperature sensor terminals 1 and 2 as shown in the figure.





[Reference data]





2. If NG, replace engine coolant temperature sensor.




Removal and Installation

ENGINE COOLANT TEMPERATURE SENSOR
Component.