STEP 1. Using scan tool MB991958, check data list item 6: Engine Coolant Temperature Sensor.
caution | To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. |
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool MB991958 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 the ignition switch to the "LOCK" (OFF) position.
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. Measure the sensor output voltage at engine coolant temperature sensor connector B-11 by backprobing.
(1) Do not disconnect the connector B-11.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 1 and ground by backprobing.- When engine coolant temperature is -20°C (-4°F), voltage should be between 3.9 and 4.5 volts.
- When engine coolant temperature is 0°C (32°F), voltage should be between 3.2 and 3.8 volts.
- When engine coolant temperature is 20°C (68°F), voltage should be between 2.3 and 2.9 volts.
- When engine coolant temperature is 40°C (104°F), voltage should be between 1.3 and 1.9 volts.
- When engine coolant temperature is 60°C (140°F), voltage should be between 0.7 and 1.3 volts.
- When engine coolant temperature is 80°C (176°F), voltage should be between 0.3 and 0.9 volt.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the measured voltage within the specified range?
Go to Step 3. Go to Step 5.
STEP 3. Check harness connector B-11 at engine coolant temperature sensor for damage.
STEP 4. Using scan tool MB991958, check data list item 6: Engine Coolant Temperature Sensor.
STEP 5. Check harness connector B-11 at engine coolant temperature sensor for damage.
STEP 6. 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.
Is the measured voltage between 4.5 and 4.9 volts?
Go to Step 8. Go to Step 7.
STEP 7. Check harness connector B-26 at ECM for damage.
STEP 8. Check the continuity at engine coolant temperature sensor harness side connector B-11.
STEP 9. Check harness connector B-26 at ECM for damage.
STEP 10. Check for harness damage between engine coolant temperature sensor connector B-11 (terminal No. 2) and ECM connector B-26 (terminal No. 27).
STEP 11. Check the engine coolant temperature sensor.
STEP 12. Check harness connector B-26 at ECM for damage.
STEP 13. Check for harness damage between engine coolant temperature sensor connector B-11 (terminal No. 1) and ECM connector B-26 (terminal No. 26).
STEP 14. 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 9 . (2) Check the diagnostic trouble code (DTC).
Is DTC P0125 set?
Retry the troubleshooting. The inspection is complete.