Engine Coolant Temperature Sensor(ECTS), installed in coolant line, senses engine coolant temperature.
With the information about engine coolant temperature, ECM performs fuel injection quantity correction, cooling fan control and glow relay operating duration control.
Especially, because ECTS signal is main variable of fuel injection quantity correction when engine is cold, sensor trouble makes starting engine difficult when engine is cold.
If engine is running when ECTS is out of order, ECM regards engine coolant temperature as 80°C. And during cranking, ECM considers engine coolant temperature as -10°C. Besides, cooling fan, which is controlled based on ECTS signal, operates at HIGH-MODE to prevent engine overheat and supplementary heater is deactivated.
P0118 is set when the voltage above 3255mV - maximum output voltage of ECTS - is detected for more than 2.0 sec. This code is due to open or short to battery in signal circuit or open in ground circuit.
Item | Detecting Condition | Possible Cause | ||
DTC Strategy | ● Voltage monitoring | ● ECTS circuit ● ECTS component | ||
Enable Conditions | ● IG KEY "ON" | |||
Threshold Value | ● Output signal above the maximum value( above 3255mV ) | |||
Diagnostic Time | ● 2.0 sec. | |||
Fail Safe | Fuel cut | NO | ● during engine operation : temperature is fixed at 80℃ at cranking : temperature is fixed at -10℃ | |
EGR Off | YES | |||
Fuel Limit | NO | |||
Check Lamp | NO | |||
Temperature | - 40℃ | - 20℃ | 0℃ | 20℃ | 40℃ |
Resistance | 48.14㏀ | 15.48±1.35㏀ | 5.790㏀ | 2.45±0.14㏀ | 1.148㏀ |
Temperature | 60℃ | 80℃ | 100℃ | 110℃ | 120℃ |
Resistance | 0.586㏀ | 0.322㏀ | 0.188㏀ | 0.147±0.002㏀ | 0.116㏀ |
Connect GDS to Data Link Connector (DLC).
Warm engine up to normal operating temperature.
Turn "OFF" electrical devices and A/C.
Monitor "ECTS" parameter on the GDS.
Specification : Current enigne coolant temperature is displayed.
Fig.1) Check if 1) incorrect value is displayed 2) coolant temperature is fixed at 80℃ suddenly during driving 3)coolant temperature is fixed at -10℃ when turning IG KEY "ON". That coolant temperature is fixed at -10℃ or 80℃ means failure of ECTS.
To prevent overheat of engine due to ECTS , if ECTS fails, cooling fan operates continuously.
Electrical systems consist of a lot of harness and connectors, poor connection of terminals can cause various problems and damge of component.
Perform checking procedure as follows.
Check damage of harness and terminals : Check terminals for contact resistance, corrosion and deformation.
Check connecting condition of ECM and component connector : Check terminal seperation, damage of locking device and connecting condition between terminal and wiring.
Disconnect the pin which requires checking at male connector and insert it to the terminal at female connector for checking connecting condition. ( after checking, reconnect the pin at correct position. )
Is the problem found?
 | ▶ Repair the trouble causing part and go to "Verification of Vehicle Repair". |
 | ▶ Go to "Signal Circuit Inspection ". |
Check signal circuit voltage
IG KEY "OFF", ENGINE "OFF".
Disconnect ECTS connector.
IG KEY "ON".
Measure the voltage between signal terminal of ECTS harness connector and chassis ground.
Specification : 4.8V~5.1V
Is the measured voltage within the specification?
| ▶ Go to "Component Inspection". |
| ▶ Go to "2.Check open in signal circuit" as follows. |
Check open in signal circuit
IG KEY "OFF", ENGINE "OFF".
Disconnect ECTS connector and ECM connector.
Check continuity between signal terminal of ECTS harness connector and ECM harness connector.
Specification : Continuity (below 1.0Ω)
Is the measured resistance within the specification?
| ▶ Go to "3.Check short to battery in signal circuit" as follows. |
| ▶ Repair open in signal circuit and go to "Verification of Vehicle Repair". |
Check short to battery in signal circuit
IG KEY "OFF", ENGINE "OFF".
Disconnect ECTS connector and ECM connector.
IG KEY "ON".
Measure the voltage between signal terminal of ECTS harness connector and chassis ground.
Specification : 0.0V~0.1V
Is the measured voltage within the specification?
| ▶ Go to "Ground Circuit Inspection". |
| ▶ Repair short to battery in signal circuit and go to "Verification of Vehicle Repair". |
IG KEY "OFF", ENGINE "OFF".
Disconnect ECTS connector.
IG KEY "ON".
Measure the voltage between signal terminal of ECTS harness connector and chassis ground. [ TEST "A" ]
Measure the voltage between signal terminal and ground terminal of ECTS harness connector. [ TEST "B" ]
( Signal terminal : Check + prove , Ground trminal : Check - prove )
Specification : [TEST "A"] Voltage - [TEST "B"] Voltage = below 200mV
Is the measured voltage within the specification?
| ▶ Go to "Component Inspection". |
| ▶ When "B" voltage is not detected : Repair open in ground circuit and go to "Verification of Vehicle Repair". ▶ When the voltage difference between "A" and "B" is above 200mV : Eliminate the causes of excessive resistance and go to "Verification of Vehicle Repair". |
IG KEY "OFF", ENGINE "OFF".
Disconnect ECTS connector.
Measure resistance between signal terminal and ground terminal of ECTS.
Specification : Refer to Specification of General Information.
Is the measured resistance at certain temperature within the specified resisance range at the temperature?
| ▶ Go to "Verification of Vehicle Rapair". |
| ▶ Replace ECTS and go to "Verification of Vehicle Repair". |
After a repair, it is essential to verify that the fault is corrected.
After connecting GDS select "Diagnostic Trouble Codes(DTCs)" mode to and then clear DTC.
Drive the vehicle within DTC Enable conditions in General information.
After selecting "Diagnostic Trouble Codes(DTCs)" mode and check DTC is recorded again.
Are any DTCs recorded ?
| ▶ Go to the DTC guide of recorded NO. in GDS. |
| ▶ System operates within specification. |
