P0128

P0128 THERMOSTAT FUNCTION





On Board Diagnosis Logic

NOTE:
If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308. P0300.
Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough.
This is due to a leak in the seal or the thermostat stuck open.









DTC Confirmation Procedure

WITH CONSULT-III

CAUTION:
Always drive vehicle at a safe speed.

NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next step.
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 fill with the fuel.
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 the indication of "COOLAN TEMP/S".
If it is below 56�C (133�F), go to following 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.
7. Drive vehicle for 10 consecutive minutes under the following conditions.





If "COOLAN TEMP/S" increases to more than 75�C (167�F) within 10 minutes, turn ignition switch
OFF because the test result will be OK.
8. Check 1st trip DTC.
9. If 1st trip DTC is detected, go to P0128.

WITH GST
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
Removal and Installation.
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.










2. If NG, replace engine coolant temperature sensor.