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DTC P0118: Engine Coolant Temperature Circuit High Input
 
 
 
 
CIRCUIT OPERATION
  • 5-volt voltage is applied to the engine coolant temperature sensor output terminal from the ECM terminal WTS via the resistor in the ECM. The ground terminal is grounded with ECM terminal WTSE.
  • The engine coolant temperature sensor is a negative temperature coefficient type of resistor. It has the characteristic that when the engine coolant temperature rises the resistance decreases.
  • The engine coolant temperature sensor output voltage increases when the resistance increases and decreases when the resistance decreases.
 
 
TECHNICAL DESCRIPTION
  • The engine coolant temperature sensor converts the engine coolant temperature to a voltage and outputs it.
  • The ECM checks whether this voltage is within a specified range.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Engine coolant temperature sensor output voltage is out of specified range.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
 
 
Check Condition
  • More than 2 seconds have passed since the power supply mode of the electric motor switch was ON.
or
  • More than 2 seconds have passed since the key-off evaporative leakage monitoring was started.
Judgment Criterion
  • Engine coolant temperature sensor output voltage has continued to be higher than 4.6 volts for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Fuel control is carried out by estimating water temperature from intake air temperature.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function-OBD-II Drive Cycle-Pattern 1 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Engine coolant temperature sensor failed.
  • Open engine coolant temperature sensor circuit or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tool:
  • MB992110: Power Plant ECU Check Harness
STEP 1. Using scan tool (M.U.T.-IIISE), check data list item 6: Engine Coolant Temperature Sensor.
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Turn on the power supply mode of the electric motor switch.
(3) Set scan tool (M.U.T.-IIISE) to the data reading mode for item 6, Engine Coolant Temperature Sensor.
  • The engine coolant temperature and temperature shown with the scan tool should approximately match.
(4) Turn off the power supply mode of the electric motor switch.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Go to Step 2.
 
STEP 2. Check the engine coolant temperature sensor.
Refer to Engine Coolant Temperature Sensor .
Is the engine coolant temperature sensor normal?
Go to Step 3.
Replace the engine coolant temperature sensor. Then go to Step 8.
 
STEP 3. Measure the sensor supply voltage at engine coolant temperature sensor harness side connector.
(1) Disconnect the engine coolant temperature sensor connector and measure at the harness side.
(2) Turn on the power supply mode of the electric motor switch.
(3) Measure the voltage between terminal WTS and ground.
  • Voltage should be between 4.5 and 4.9 volts.
(4) Turn off the power supply mode of the electric motor switch.
Is the measured voltage between 4.5 and 4.9 volts?
Go to Step 5.
Go to Step 4.
 
STEP 4. Measure the sensor supply voltage at ECM connector by using power plant ECU check harness special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2) Disconnect the engine coolant temperature sensor connector.
(3) Turn on the power supply mode of the electric motor switch.
(4) Measure the voltage between terminal WTS and ground.
  • Voltage should be between 4.5 and 4.9 volts.
(5) Turn off the power supply mode of the electric motor switch.
Is the measured voltage between 4.5 and 4.9 volts?
Repair or replace the connector(s), or check and repair the harness of open circuit in WTS line between engine coolant temperature sensor connector and ECM connector. Then go to Step 7.
Go to Step 7.
 
STEP 5. Check the continuity at engine coolant temperature sensor harness side connector.
(1) Disconnect the engine coolant temperature sensor connector and measure at the harness side.
(2) Check for the continuity between terminal WTSE and ground.
  • Continuity (2 ohms or less)
Does continuity exist?
Go to Step 7.
Go to Step 6.
 
STEP 6. Check of open circuit in WTSE line between engine coolant temperature sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 7.
Repair the connector(s) or wiring harness. Then go to Step 8.
 
STEP 7. Using scan tool (M.U.T.-IIISE), check data list item 6: Engine Coolant Temperature Sensor.
(1) Turn on the power supply mode of the electric motor switch.
(2) Set scan tool (M.U.T.-IIISE) to the data reading mode for item 6, Engine Coolant Temperature Sensor.
  • The engine coolant temperature and temperature shown with the scan tool should approximately match.
(3) Turn off the power supply mode of the electric motor switch.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Replace the ECM (Refer to Removal and Installation ). Then go to Step 8.
 
STEP 8. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0118 set?
Retry the troubleshooting.
The inspection is complete.