Inspection Procedure 4

INSPECTION PROCEDURE 4: The Ambient Air Temperature Display Shows "COM ERROR" Or "- °C (- °F)." (Middle Grade Type Or Vehicles With Mitsubishi Multi Communication System)

CIRCUIT OPERATION
The A/C-ECU receives information on ambient air temperature from the ambient air temperature sensor. Then the information is sent to the multi-center display unit (middle grade type or Vehicles With Mitsubishi Multi Communication system) via CAN communication.

TECHNICAL DESCRIPTION (COMMENT)
If the A/C-ECU has not informed an ambient air temperature via the CAN communication for 60 seconds or more, "COM ERROR" appears on the screen. If the multi-center display unit (middle grade type) can not receive correct information from the ambient air temperature sensor at all, "- °C (-°F)" will be shown.

TROUBLESHOOTING HINTS
- Malfunction of multi-center display unit (middle grade type or Vehicles With Mitsubishi Multi Communication system)
- Malfunction of A/C-ECU
- Malfunction of Ambient air temperature sensor.
- 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: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line

Use scan tool MB991958 to diagnose the CAN bus lines.




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 Controller Area Network (CAN), Diagnosis-Can Bus Diagnostic Chart). After diagnosing the CAN bus lines, go to Step 3.

STEP 2. Using scan tool MB991958, read A/C diagnostic trouble code.

Check if an A/C system DTC is set.

Q: Is the DTC set?

YES : Refer to Heater and A/C, Manual A/C Diagnosis - Diagnostic Trouble Code Chart ]Low Type[ or Diagnostic Trouble Code Chart ]Middle Type[ or Auto A/C Diagnostic Trouble Code Chart and then go to Step 3.

NO : Replace multi-center display unit (middle grade type) and then go to Step 3.

STEP 3. Retest the system

Check if the ambient air temperature operation screen is displayed normally.

Q: Is the check result satisfactory?

YES : The procedure is complete.

NO : Go to Step 1.