P0128

P0128 THERMOSTAT FUNCTION

DTC Logic


DTC DETECTION 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 leakage in the seal or the thermostat being stuck open.






DTC CONFIRMATION PROCEDURE


1. PRECONDITIONING

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 51�C (124�F).
-Before performing the following procedure, do not add fuel.
- GO TO 2.

2. PERFORM DTC CONFIRMATION PROCEDURE

WITH CONSULT
1.Turn A/C switch OFF.
2.Turn blower fan switch OFF.
3.Turn ignition switch ON.
4.Select "COOLANT TEMP/S" in "DATA MONITOR" mode with CONSULT.
5.Check the indication of "COOLANT TEMP/S".
If it is below 51�C (124�F), go to next step.
If it is above 51�C (124�F), cool engine down to less than 51�C (124�F). Then go to next step.
6.Start engine and drive vehicle for 10 consecutive minutes under the following conditions.






CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If "COOLANT TEMP/S" increases to more than 70�C (158�F) within 10 minutes, turn ignition switch
OFF because the test result will be OK.
7.Check 1st trip DTC.
WITH GST
Follow the procedure "With CONSULT" above.
Is 1st trip DTC detected?
YES- Proceed to .
NO- INSPECTION END


Diagnosis Procedure


1. CHECK ENGINE COOLANT TEMPERATURE SENSOR

.
Is the inspection result normal?
YES- GO TO 2.
NO- Replace engine coolant temperature sensor. Exploded View.

2. CHECK THERMOSTAT

Remove and Check the thermostat. Removal And Installation and Inspection.
Is the inspection result normal?
YES- INSPECTION END
NO- Replace thermostat. Exploded View.


Component Inspection (Engine Coolant Temperature Sensor)


1. CHECK ENGINE COOLANT TEMPERATURE (ECT) SENSOR

1.Turn ignition switch OFF.
2.Disconnect ECT sensor harness connector.
3.Remove ECT sensor. Exploded View.





4.Check resistance between ECT sensor terminals by heating with hot water as shown in the figure.





Is the inspection result normal?
YES- INSPECTION END
NO- Replace ECT sensor. Exploded View.