P0128

DTC P0128 THERMOSTAT FUNCTION





On Board Diagnosis Logic

NOTE:
If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303 or P0304, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304. 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 turn ignition switch OFF and wait at least 10 seconds before conducting the next test.
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 53�C (127�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 53�C (127�F), go to following step.
If it is above 53�C (127�F), cool down the engine to less than 53�C (127�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 SEE Diagnosis Procedure.

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




Diagnosis Procedure
1.CHECK ENGINE COOLANT TEMPERATURE SENSOR
SEE Component Inspection.
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.





[Reference data]





2. If NG, replace engine coolant temperature sensor.




Removal and Installation

ENGINE COOLANT TEMPERATURE SENSOR
Removal And Installation.