P0118
COMPONENT 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 ECM is supplied to the ECTS via a resistor in the ECM. That is, the resistor in the ECM 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 ECM increases the fuel injection duration and controls the ignition timing using the information of engine coolant temperature to avoid engine stalling and improve drivability.
DTC DESCRIPTION
Checking output signals from ECTS every 80 sec. under detecting condition, if an output signal is above 4.9V for more than 40 sec., PCM sets P0118. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC DETECTING CONDITION
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.
SPECIFICATION
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1. Check DTC Status
(1) Connect scantool to Data Link Connector(DLC).
(2) IG "ON".
(3) Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
(4) Read "DTC Status" parameter.
(5) Is parameter displayed "Present fault"?
YES
> Go to "Terminal and connector inspection" procedure.
NO
> 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, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
TERMINAL AND 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 voltage
(1) IG "OFF" and disconnect ECTS connector.
(2) IG "ON" and ENG "OFF"
(3) Measure voltage between terminal 3 of ECTS harness connector and chassis ground.
Specification : Approx. 5V
(4) Is the measured voltage within specification ?
YES
> Go to "Ground Circuit Inspection" procedure.
NO
> If voltage is 0V, go to "Check open in harness" as follows. If it is more than 5.1V, go to "Check short to battery in harness" as follows
2. Check short to battery in harness
(1) IG "OFF" and disconnect ECTS connector and PCM connector.
(2) Measure resistance between terminals 2 and 3 of ECTS harness connector.
Specification : Infinite
(3) Is the measured resistance within specification?
YES
> Go to "Component Inspection" procedure.
NO
> Repair short to battery in harness, and go to "Verification of Vehicle Repair" procedure.
3. Check open in harness
(1) IG "OFF" and disconnect ECTS connector and PCM connector.
(2) Measure resistance between terminal 3 of ECTS harness connector and terminal C201-2 (7) of PCM harness connector.
Specification : Below 1Ohms
(3) Is the measured resistance within specification?
YES
> Go to "Ground Circuit Inspection" procedure.
NO
> Repair open in harness, and go to "Verification of Vehicle Repair" procedure.
GROUND CIRCUIT INSPECTION
1. IG "OFF" and disconnect ECTS connector.
2. Measure voltage between terminal 3 of ECTS harness connector and chassis ground.
3. Measure voltage between terminals 1 and 3 of ECTS harness connector.
Specification : Voltage difference between measurement "A" and "B" is below 200mV.
4. Is the measured voltage within specification?
YES
> Go to "Component Inspection" procedure.
NO
> Repair open or contact resistance in harness, and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Check ECTS
(1) IG "OFF" and disconnect ECTS connector.
(2) Measure resistance between terminals 1 and 3 of ECTS connector.(Component side)
Specificaton :
(3) Is the measured resistance within specification?
YES
> Go to "Check PCM" as follows.
NO
> Substitute with a known - good ECTS and check for proper operation. If the problem is corrected, replace ECTS and go to "Verification of Vehicle Repair" procedure.
2. Check PCM
(1) IG "OFF" and connect scantool.
(2) Connect probe to terminal 3 of ECTS harness connector.
(3) IG "ON" and ENG "OFF" and simulation Function on scantool.
(4) Simulate voltage at terminal 3 of ECTS harness connector.
(5) Does the signal value of ECT sensor change according to simulation voltage ?
YES
> 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
> 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 rediness test have been verified as " Complete "
5. Are any DTCs present ?
YES
> Go to the applicable troubleshoooting procedure.
NO
> System is performing to specification at this time.