P0128
DTC P0128 THERMOSTAT FUNCTIONOn Board Diagnosis Logic
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 leak in the seal or the thermostat stuck open.
DTC Confirmation Procedure
NOTE: If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 5 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 70 °C (158 °F).
WITH CONSULT-II
1. Replace thermostat with new one. If an incorrect thermostat is used, the MIL may come on.
2. Turn ignition switch ON.
3. Select "COOLAN TEMP/S" in "DATA MONITOR" mode with CONSULT-II.
4. Check that the "COOLAN TEMP/S" is above 70 °C (158 °F).
If it is below 70 °C (158 °F), Go to following step.
If it is above 70 °C (158 °F), stop engine and cool down the engine to less than 70 °C (158 °F), then retry from step 1.
5. Drive vehicle for 10 consecutive minutes under the given conditions.
VHCL SPEED SE 80 - 120 km/h (50 - 75 MPH)
If 1st trip DTC is detected, Go to "Diagnostic Procedure" below.
WITH GST
Follow the procedure "WITH CONSULT-II" above.
Diagnostic Procedure:
Diagnostic Procedure
Component Inspection
ENGINE COOLANT TEMPERATURE SENSOR
1. Check resistance as shown.
2. If NG, replace engine coolant temperature sensor.