Inspection Procedure 10

INSPECTION PROCEDURE 10: Engine coolant temperature gauge does not work (other meters work)

CIRCUIT OPERATION
The engine coolant temperature sensor sends signal to the combination meter via the ECM [M/T] or PCM [A/T] and the CAN bus line.

TECHNICAL DESCRIPTION (COMMENT)
If only the engine coolant temperature gauge does not operate, the ECM [M/T] or PCM [A/T] system, the combination meter, the wiring harness or its connector may be defective.

TROUBLESHOOTING HINTS
- Malfunction of the ECM [M/T] or PCM [A/T]
- Malfunction of the combination meter
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991824, diagnose the CAN bus line.







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. Turn the ignition switch to "ON" position.
2. Diagnose the CAN bus line.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : Go to Step 2.

NO : Repair the CAN bus lines.

STEP 2. Using scan tool MB991958, read MFI diagnostic trouble code.

Check if an MFI system diagnostic trouble code is set.







1. Turn the ignition switch to "ON" position.
2. Read the diagnostic trouble code.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Diagnose the MFI system by referring to MFI Diagnosis - Diagnostic Trouble Code Chart [2.4 L engine] Diagnostic Trouble Code Descriptions or MFI Diagnosis - Diagnostic Trouble Code Chart [3.8 L engine] Diagnostic Trouble Code Descriptions.

NO : Go to Step 3.

STEP 3. Using scan tool MB991958, check data list.







1. Turn the ignition switch to "ON" position.
2. Set scan tool MB991958 to the data reading mode.
- Item 08: Engine coolant temperature
- Engine coolant temperature and M.U.T.-III displayed values agree with each other.

3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result normally?

YES : It can be assumed that this malfunction is intermittent.

NO : Go to Step 4.

STEP 4. Using scan tool MB991958, check actuator test.







1. Turn the ignition switch to "ON" position.
2. Set scan tool MB991958 to the actuator test mode.

- Item 14: Water temperature gauge: 0° C (32° F)
- Water temperature gauge shows 0° C (32° F)

- Item 15: Water temperature gauge: 85° C (185° F)
- Water temperature gauge shows 85° C (185° F)

- Item 16: Water temperature gauge: 126° C (259° F)
- Water temperature gauge shows 126° C (259° F)

3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result normally?

YES : Go to Step 5.

NO : Replace the combination meter.

STEP 5. Retest the system.

Check to see that the engine coolant temperature gauge operates normally.

Q: Is the check result satisfactory?

YES : The procedure is complete. (If no malfunctions are found in all steps, an intermittent malfunction is suspected.)

NO : Replace the combination meter.