DIAGNOSIS Required Special Tools: • MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: V.C.I. MB991827: USB Cable MB991911: Main Harness B

STEP 1. Using scan tool MB991958, check data list item 21: Engine Coolant Temperature Sensor.

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 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 GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions . NO: Go to Step 2.

STEP 2. Check harness connector B-107 at the engine coolant temperature sensor for damage.

Q: Is the harness connector in good condition? YES: Go to Step 3. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 3. Measure the sensor supply voltage at engine coolant temperature sensor harness side connector B-107.

(1) Disconnect connector B-107 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.

STEP 4. Measure the sensor supply voltage at ECM connector C-115 <M/T> or PCM connector C-118 <A/T> by backprobing.

(1) Do not disconnect the ECM connector C-115 <M/T> or PCM connector C-118 <A/T>. (2) Disconnect the engine coolant temperature sensor connector B-107. (3) Turn the ignition switch to the "ON" position.

(4) Measure the voltage between terminal No. 83 <M/T> or No. 44 <A/T> 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.

STEP 5. Check harness connector C-115 at ECM <M/T> or harness connector C-118 at PCM <A/T> for damage.

Q: Is the harness connector in good condition? YES: Repair harness wire between engine coolant temperature sensor connector B-107 and ECM connector C-115 <M/T> or PCM connector C-118 <A/T> because of open circuit. Then go to Step 11. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 6. Check harness connector C-115 at ECM <M/T> or harness connector C-118 at PCM <A/T> for damage.

Q: Is the harness connector in good condition? YES: Replace the ECM or PCM. Then go to Step 11. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 7. Check for continuity at engine coolant temperature sensor harness side connector B-107.

(1) Disconnect connector B-107 and measure at the harness side.

(2) Check for the continuity between terminal No. 2 and ground. • Should be less than 2 ohms. Q: Does continuity exist? YES: Go to Step 10. NO: Go to Step 8.

STEP 8. Check harness connector C-115 at ECM <M/T> or harness connector C-118 at PCM <A/T> for damage.

Q: Is the harness connector in good condition? YES: Go to Step 9. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 9. Check for open circuit between engine coolant sensor connector B-107 (terminal No. 2) and ECM connector C-115 (terminal No. 92) <M/T> or PCM connector C-118 (terminal No. 57) <A/T>.

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-107. (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 kΩ [at -20°C (-4°F)] 5.1 - 6.5 kΩ [at 0°C (32°F)] 2.1 - 2.7 kΩ [at 20°C (68°F)] 0.9 - 1.3 kΩ [at 40°C (104°F)] 0.48 - 0.68 kΩ [at 60°C (140°F)] 0.26 - 0.36 kΩ [at 80°C (176°F)]

(4) Apply 3MTM 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 N·m (22 ± 7 ft-lb) 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 go to Step 11.