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 powertrain control module and the CAN bus line
TECHNICAL DESCRIPTION (COMMENT)
If only the engine coolant temperature gauge does not operate, the powertrain control module system, the combination meter, the wiring harness or its connector may be defective
TROUBLESHOOTING HINTS
- Malfunction of the powertrain control module
- 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 (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (VCI)
- MB991827: MUT-III USB Cable
- MB991910: MUT-III Main Harness A (Vehicles with CAN communication system)
STEP 1 Using scan tool MB991824, diagnose the CAN bus line
1. Connect scan tool MB991958 to the data link connector
2. Turn the ignition switch to "ON" position
3. Diagnose the CAN bus line
Q: Is the check result satisfactory?
YES: Go to Step 2
NO: Repair the CAN bus lines (Refer to Diagnosis in Information Bus, - Can Bus Diagnostic Chart) On completion, go to Step 5
STEP 2 Using scan tool MB991958, read MFI diagnostic trouble code
Check if an MFI system DTC is set
Q: Is the DTC set?
YES: Diagnose the MFI system by referring to MFI Diagnosis - Diagnostic Trouble Code Chart <24L ENGINE> or MFI Diagnosis - Diagnostic Trouble Code Chart <38L ENGINE> On completion, in Computer control systems. go to Step 5
NO: Go to Step 3
STEP 3 Using scan tool MB991958, check data list
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
- Item 8C: Engine coolant temperature gauge
- The voltage should equal battery positive voltage
- Item 8E: Coolant Temparature confirmation flag
- The voltage should equal battery positive voltage
4. 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 Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.
NO: Go to Step 4
STEP 4 Using scan tool MB991958, check actuator test
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 actuator test mode
- Item 88: Engine coolant Temp gauge: 0 degree C (32 degrees F)
- Engine coolant temperature gauge shows 0 degree C (32 degrees F)
- Item 89: Engine coolant Temp gauge: 85 degrees C (185 degrees F)
- Engine coolant temperature gauge shows 85 degrees C (185 degrees F)
- Item 8A: Engine coolant Temp gauge: 126 degrees C (259 degrees F)
- Engine coolant temperature gauge shows 126 degrees C (259 degrees F) 4 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 Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction)
NO: Replace combination meter and then go to step 1