P0128
DTC P0128The Thermostat is a mechanical device located in an engine coolant passage the coolant has reached a specified temperature it expands and contracts according to temperature, thereby controlling the passage of coolant into the radiator.
DTC DESCRIPTION
If the engine coolant temperature does not reach the specified value within the allocated period of time, the PCM determines that a malfunction exists and a DTC is stored. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC Detecting Condition:
DTC DETECTING CONDITION
Signal Waveform And Data:
SIGNAL WAVEFORM AND DATA
The output signals of IATS& ECTS change smoothly without any rapid changes. Those have almost same characteristic signal during the early period after start. It means that the temperatures of intake air and engine coolant are depended on the temperature of atmosphere. Meanwhile, during the warming up, the output signal of ECTS is going up increasingly. but, the output signal of IATS changes a little bit. even it may not change almost. It means that the heat of engine does not affect on the temperature of intake air.
MONITOR SCANTOOL DATA
1. Engine "OFF"
2. Monitor Engine Coolant Temperature Sensor parameter on Current data
3. Is the measured ECTS parameter displayed within specifications?
YES - Fault is intermittent caused by poor contact in the sensor s and/or PCM`s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO - Go to "Component Inspection" procedure
COMPONENT INSPECTION
1. Check Thermostat
a. Check cooling system coolant level and fill if low.
b. Check for a proper cooling system operation. Especially check that cooling and condenser fan working normally.
c. Remove the thermostat and check the following items: (1) Stuck or damaged (2) Verify the temperature at which the valve is open : 80 - 84 °C (176 - 183.2 °F)
d. Has a problem been found?
YES - Substitute with a known - good Thermostat and check for proper operation. If the problem is corrected, replace Thermostat and go to "Verification of Vehicle Repair" proprocedure.
NO - Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
NOTE: There is a memory reset function on Scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions
4. Monitor that all readiness test have been verified as "Complete".
5. Are any DTCs present?
YES - Go to the applicable troubleshooting procedure.
NO - System is performing to specification at this time.