P0118
DTC P0118 ENGINE COOLANT TEMPERATURE CIRCUIT HIGH INPUTComponent Location:
GENERAL DESCRIPTION
The Engine Coolant Temperature Sensor (ECTS) is located in the engine coolant passage of the cylinder head for detecting the engine coolant temperature. The ECTS uses a thermistor whose resistance changes with the temperature. The electrical resistance of the ECTS decreases as the temperature increases, and increases as the temperature decreases. The reference 5 V in the PCM is supplied to the ECTS via a resistor in the PCM. That is, the resistor in the PCM and the thermistor in the ECTS are connected in series. when the resistance value of the thermistor in the ECTS changes according to the engine coolant temperature, the output voltage also changes.During cold engine operation the PCM increases the fuel injection duration and controls the ignition timing using the information of engine coolant temperature to avoid engine stalling and improve driveablity.
DTC DESCRIPTION
PCM sets DTC P0118 if the PCM detects signal voltage lower than the possible range of a properly operating ECTS.
DTC Detecting Condition:
Specification:
Schematic Diagram:
SCHEMATIC DIAGRAM
SIGNAL WAVEFORM & DATA
This figure shows the wave form at terminal 4 of ECTS at idle rpm.
1. In case the voltage of ECTS is always 4 V.
Possible cause : Open ground circuit Open inner circuit of component
2. In case, when engine is cold,the voltage is below 0.5 V.
Possible cause: Short between PCM and sensor Faulty PCM
When checking the wave form,watch carefully if there is any sudden change in signal.
The ECTS and IATS signals should be smooth and continuous without any sudden changes. When the engine is cold, the ECTS and IATS signals should look similar, depending on the ambient air temperature. After warm-up, the IATS signal should not changes significantly, while the ECTS signal should drop. This indicates that the normal increase of the engine coolant temperature is larger than the normal increase of the intake air temperature as the engine warms up.
MONITOR DTC STATUS
This is the inspection procedure to determine whether it is present DTC or memoried one by monitoring the current signal or by using the function of oscilloscope with Hi-scan pro.
1. Connect scantool to Data Link Connector(DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor the "ECTS signal" parameter on the scantool.
NOTE: If the output data changes as temperature changes, the sensor is good.
If the ECTS output is in inverse proportion to water temperature, the sensor is normal.
Service standard
When ECT is 0 °C(32 °F): 4.27 ± 0.3 V
When ECT is 20 °C(68 °F): 3.44 ± 0.3 V
When ECT is 40 °C(104 °F): 2.72 ± 0.3 V
When ECT is 80 °C(176 °F): 1.25 ± 0.3 V
4. Is 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 then go to "Verification of Vehicle Repair" procedure.
NO: Go to "W/Harness Inspection" procedure
TERMINAL & CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination,deterioration, or damage
3. Has a problem been found?
YES: Repair as necessary and go to "Verification of vehicle Repair" procedure.
NO: Go to "Signal circuit inspection" procedure.
SIGNAL CIRCUIT INSPECTION
1. Check for short to ground in harness
1. Ignition "OFF"
2. Disconnect ECT sensor connector and PCM connector.
3. Ignition "ON" & Engine "OFF"
4. Measure resistance between terminal 1 of sensor harness connector and chassis ground.
5. Measure resistance between terminal 1 and 2 of sensor harness connector.
Specification: infinite
6. Is measure resistance within Specification?
YES: Go to "Component Inspection" procedure.
NO:
- Short circuit between ECTS signal circuit and ground circuit.
- Short chassis ground between ECTS harness connector and PCM harness connector.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
COMPONENT INSPECTION
The resistence check of ECTS component is for finding whether open circuit is in the component.
1. Check ECTS
1. Measure resistance between terminal 1 and 2 of sensor connector(To sensor side)
Specification:
20 °C(68 °F) : 2.27 - 2.73 kOhms
80 °C(176 °F): 0.29 - 0.32 kOhms
2. Does each resistance indicate continuity circuit?
YES: Go to Check PCM" as below.
NO:
- Open circuit ECTS.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
2. Check PCM
The purpose of checking ECM is to determine whether there is any malfunction of PCM.
1. Ignition "OFF"
2. Connect Scantool and Engine "ON"
3. Select simulation function on scantool.
4. Simulate voltage at terminal 1 of ECT sensor signal connector
5. Verify ECTS voltage to change while raising or lowering simulation voltage with scan tool within 0.5 - 3.5 V
Specification: If the data is changeable as simulation voltage changes, it's OK
6. Is ECT sensor signal value changed according to simulation voltage?
YES: Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO: Substitute with a known-good PCM and check for proper operation. If the problem is corrected, replace PCM and then go to "Verification of Vehicle Repair" procedure.
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 rediness 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.