P0118
Engine Coolant Temperature Sensor Circuit:
Connectors:
CIRCUIT OPERATION
- 5-volt voltage is applied to the engine coolant temperature sensor output terminal (terminal No.1) from the ECM (terminal No.44)
- 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 resistor decreases.
- The engine coolant temperature sensor output voltage increases when the resistor increases and decreases when the resistor decreases.
TECHNICAL DESCRIPTION
- The engine coolant temperature sensor converts the engine coolant temperature to a voltage and output it.
- The ECM
DTC SET CONDITIONS
Check Conditions
- Two seconds or more have passed since the staring sequence was completed.
Judgement Criteria
- Engine coolant temperature sensor output voltage has continued to be 4.6 volts or higher [corresponding to a coolant temperature of -45 °C (-49 °F) or lower for 2 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Engine coolant temperature sensor failed.
- Open or shorted engine coolant temperature sensor circuit, or loose connector.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
CAUTION
To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991502 to the data reading mode for item 21, Engine Coolant Temperature Sensor.
- The engine coolant temperature and temperature shown with the scan tool should approximately match.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to INTRODUCTION, How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. Check connector B-11 at the engine coolant temperature sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 3.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 11.
STEP 3. Measure the sensor supply voltage at engine coolant temperature sensor harness side connector B-11.
1. Disconnect the connector B-11 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.1 and ground.
- Voltage should be between 4.5 and 4.9 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.5 and 4.9 volts?
YES: Go to Step 7.
NO: Go to Step 4.
Connectors:
STEP 4. Measure the sensor supply voltage at ECM connector C-118
1. Do not disconnect the ECM connector C-118
2. Disconnect the engine coolant temperature sensor connector B-11.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal No.44 and ground by backprobing.
- Voltage should be between 4.5 and 4.9 volts.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.5 and 4.9 volts?
YES: Go to Step 5.
NO: Go to Step 6.
Connectors:
STEP 5. Check connector C-118 at ECM
Q: Is the connector in good condition?
YES: Repair harness wire between engine coolant temperature sensor connector B-11 and ECM connector C-118
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 11.
Connectors:
STEP 6. Check connector C-118 at ECM
Q: Is the connector in good condition?
YES: Replace the ECM or PCM. Then go to Step 11.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 11.
STEP 7. Check the continuity at engine coolant temperature sensor harness side connector B-11.
1. Disconnect the connector B-11 and measure at the harness side.
2. Check for the continuity between terminal No.2 and ground.
Should be less than 2 ohms.
Q: Is the continuity normal?
YES: Go to Step 10.
NO: Go to Step 8.
Connectors:
STEP 8. Check connector C-118 at ECM
Q: Is the connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 11.
Connectors:
STEP 9. Check for open circuit between engine coolant sensor connector B-11 (terminal No.2) and ECM connector C-118 (terminal No.49)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 11.
NO: Repair it. Then go to Step 11.
STEP 10. Check the engine coolant temperature sensor.
1. Disconnect the engine coolant temperature sensor connector B-11.
2. Remove the engine coolant temperature sensor.
3. With the temperature sensing portion of engine coolant temperature sensor immersed in hot water, check resistance.
Standard value:
14 - 17 kohms @ -20 °C (-4 °F)
5.1 - 6.5 kohms @ 0 °C (32 °F)
2.1 - 2.7 kohms @ 20 °C (68 °F)
0.9 - 1.3 kohms @ 40 °C (104 °F)
0.48 - 0.68 kohm @ 60 °C (140 °F)
0.26 - 0.36 kohm @ 80 °C (176 °F)
4. Apply 3M(TM) AAD part number 8731 or equivalent on the screw section of the engine coolant temperature sensor.
5. Install the engine coolant temperature sensor, and tighten to the specified torque.
Tightening torque: 29 ± 10 Nm (22 ± 7 ft. lbs.)
Q: Is the resistance at the standard value?
YES: Replace the ECU or PCM. Then go to Step 11.
NO: Replace the engine coolant temperature sensor. Then goto Step 11.
STEP 11. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0118 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.