Inspection Procedure 3

INSPECTION PROCEDURE 3: The A/C Display Shows "COMMUNICATION ERROR", And Then Can Not Proceed To Next Screen. (Middle Grade Type Or Vehicles With Mitsubishi Multi Communication System)

CIRCUIT OPERATION
The multi-center display unit (middle grade type or Vehicles With Mitsubishi Multi Communication system) receives information on current A/C operation condition from the A/C-ECU via CAN bus lines.

TECHNICAL DESCRIPTION (COMMENT)
The multi-center display unit (middle grade type or Vehicles With Mitsubishi Multi Communication system) will show "COMMUNICATION ERROR" message if it has received abnormal data from the A/C-ECU via CAN communication for 60 seconds or more. Then the A/C operation screen, which is based on the last normal information, continues to be shown. If the communication returns to normal, "COMMUNICATION ERROR" message will disappear and the A/C operation screen will return to normal.

TROUBLESHOOTING HINTS
- Malfunction of multi-center display unit (middle grade type or Vehicles With Mitsubishi Multi Communication system)
- Malfunction of A/C-ECU
- 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, 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 Heater and A/C, 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 A/C operation screen is displayed normally.

Q: Is the check result satisfactory?

YES : The procedure is complete.

NO : Go to Step 1.