INSPECTION PROCEDURE A-4: Communication With The Front-ECU Is Not Possible.: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB991958: Scan Tool (MUT-III Sub Assembly)
  • MB991824: Vehicle Communication Interface (V.C.I.)
  • MB991827: MUT-III USB Cable
  • MB991911: MUT-III Main Harness B
• MB991813: SWS monitor kit
  • MB991806: SWS monitor cartridge
  • MB991812: SWS monitor harness (for column-ECU)
  • MB991922: Probe harness

1. STEP 1. Use scan tool MB991958 to select "ECU COMM Check" on the SWS monitor display. 

   Check the ETACS-ECU.

   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. Connect special tool MB991911 before connecting special tool MB991812. Be sure to connect special tool MB991806 after turning on special tool MB991824.
   1. Connect the special tool. Refer to "HOW TO CONNECT SWS MONITOR ."
   2. Turn the ignition switch to the "LOCK" (OFF) position.
   3. Operate scan tool MB991958 according to the procedure below to display "ECU COMM Check."
      1. Select "Interactive Diagnosis."
      2. Select "System select."
      3. Select "SWS."
      4. Select "SWS MONITOR."
      5. Select "ECU COMM Check."
   4. Scan tool MB991958 should show "OK" on the "ECU COMM Check" menu for the "ETACS ECU" menu.

   Q: Is "OK" displayed on the "ETACS ECU" menu? 

   • YES :  Go to Step 2.
   • NO :  Refer to "INSPECTION PROCEDURE A-3: COMMUNICATION WITH THE ETACS-ECU IS NOT POSSIBLE ".
   Fig 1: Connecting Special Tool To Data Link Connector

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. STEP 2. Check the front-ECU connector A-10X for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is the front-ECU connector A-10X in good condition? 

   • YES :  Go to Step 3.
   • NO :  Repair or replace the damaged component(s). Refer to HARNESS CONNECTOR INSPECTION . The system should communicate with the front-ECU normally.
   Fig 2: Identifying Front-ECU Connector A-10X Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. STEP 3. Check the battery power supply circuit to the front-ECU. Measure the voltage at front-ECU connector A-10X. 
   1. Disconnect front-ECU connector A-10X and measure the voltage available at the relay box side of the connector.
      Fig 3: Identifying Front-ECU Connector A-10X

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   2. Measure the voltage between terminal 7 and ground.
      • The voltage should equal approximately 12 volts (battery positive voltage).

   Q: Is the measured voltage approximately 12 volts (battery positive voltage)? 

   • YES :  Go to  Step 5.
   • NO :  Go to Step 4.
   Fig 4: Measuring Voltage Between Terminal 7 And Ground

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. STEP 4. Check the wiring harness between front-ECU connector A-10X (terminal 7) and the battery. 

   Q: Is the wiring harness between front-ECU connector A-10X (terminal 7) and the battery in good condition? 

   • YES :  No action is necessary and testing is complete.
   • NO :  The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The system should communicate with the front-ECU normally.
   Fig 5: Identifying Front-ECU Connector A-10X Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. STEP 5. Check the front-ECU connector A-11X for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is front-ECU connector A-11X in good condition? 

   • YES :  Go to Step 6.
   • NO :  Repair or replace the damaged component(s). Refer to HARNESS CONNECTOR INSPECTION . The system should communicate with the front-ECU normally.
   Fig 6: Identifying Front-ECU Connector A-11X Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
6. STEP 6. Check the ground circuit to the front-ECU. Measure the resistance at front-ECU connector A-11X. 
   1. Disconnect front-ECU connector A-11X and measure the resistance available at the relay box side of the connector.
      Fig 7: Identifying Front-ECU Connector A-11X

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   2. Measure the resistance value between terminal 31 and ground.
      • The resistance should equal 2 ohms or less.

   Q: Is the measured resistance 2 ohms or less? 

   • YES :  Go to  Step 8.
   • NO :  Go to Step 7.
   Fig 8: Measuring Resistance Value Between Terminal 31 And Ground

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
7. STEP 7. Check the wiring harness between front-ECU connector A-11X (terminal 31) and the ground. 

   Q: Is the wiring harness between front-ECU connector A-11X (terminal 31) and ground in good condition? 

   • YES :  No action is necessary and testing is complete.
   • NO :  The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The system should communicate with the front-ECU normally.
   Fig 9: Identifying Front-ECU Connector A-11X Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
8. STEP 8. Check the ETACS-ECU connector C-228 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is ETACS-ECU connector C-228 in good condition? 

   • YES :  Go to Step 9.
   • NO :  Repair or replace the damaged component(s). Refer to HARNESS CONNECTOR INSPECTION . The system should communicate with the front-ECU normally.
   Fig 10: Identifying ETACS-ECU Connector C-228 Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
9. STEP 9. Check the wiring harness between front-ECU connector A-11X (terminal 22) and ETACS-ECU connector C-228 (terminal 59). 
   Fig 11: Identifying Front-ECU Connector A-11X Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   Fig 12: Identifying ETACS-ECU Connector C-228 Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   NOTE: Also check intermediate connector C-129 and joint connector C-101 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-129 or joint connector C-101 is damaged, repair or replace the damaged component(s) as described in HARNESS CONNECTOR INSPECTION .

   Q: Is the wiring harness between front-ECU connector A-11X (terminal 22) and ETACS-ECU connector C-228 (terminal 59) in good condition? 

   • YES :  Go to Step 10.
   • NO :  The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The system should communicate with the front-ECU normally.
   Fig 13: Identifying Intermediate Connector C-129 And Joint Connector C-101 Terminals

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
10. STEP 10. Replace the front-ECU. 
    1. Replace the front-ECU.
    2. The system should communicate with the front-ECU normally.

    Q: Can the system communicate with the front-ECU? 

    • YES :  No action is necessary and testing is complete.
    • NO :  Replace the ETACS-ECU. The system should communicate with the front-ECU normally.