INSPECTION PROCEDURE 1: Communication with Scan Tool MB991502 is Impossible.: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB991502: Scan Tool (MUT-II)

1. STEP 1. Check scan tool MB991502 communicates with the MFI system and MFI system DTC output other than P1610. 

   Q: Can scan tool MB991502 communicate with the MFI system? Does MFI system DTC other than P1610 reset? 

   YES  : Refer to MFI Diagnosis < 2.4L ENGINE > or MFI Diagnosis < 3.0L ENGINE >.

   NO:  Go to Step 2.

2. STEP 2. Check the immobilizer-ECU power supply circuit by backprobing. 
   1. Do not disconnect immobilizer-ECU connector C-128.
   2. Turn the ignition switch to the "ON" position.
      Fig 1: Identifying Connector C-128

      Courtesy of DAIMLERCHRYSLER CORPORATION
   3. Measure the voltage between terminal 7 and ground by backprobing.

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

   YES  : Go to  Step 5.

   NO:  Go to Step 3.

   Fig 2: Measuring Voltage Between Terminal 7 And Ground

   Courtesy of DAIMLERCHRYSLER CORPORATION
3. STEP 3. Check immobilizer-ECU connector C-128 and MFI relay connector A-18X for damage. 

   Q: Are immobilizer-ECU connector C-128 and MFI relay connector A-18X damaged? 

   YES  : Repair or replace the connector(s). Refer to , HARNESS CONNECTOR INSPECTION . Confirm that scan tool MB991502 communicates normally.

   NO:  Go to Step 4.

   Fig 3: Identifying Connector A-18X

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 4: Identifying Connector C-128

   Courtesy of DAIMLERCHRYSLER CORPORATION
4. STEP 4. Check the wiring harnesses between immobilizer-ECU connector C-128 (terminal 7) and MFI relay connector A-18X (terminal 4). 
   Fig 5: Identifying Connector A-18X

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 6: Identifying Connectors C-25, C-128

   Courtesy of DAIMLERCHRYSLER CORPORATION
   NOTE: Also check the intermediate connector C-25. If intermediate connector C-25 is damaged, repair or replace the connector. Refer to , HARNESS CONNECTOR INSPECTION .

   Q: Are the wiring harnesses between immobilizer-ECU connector C-128 (terminal 7) and MFI relay connector A-18X (terminal 4) damaged? 

   YES  : Replace the wiring harness(es). Confirm that scan tool MB991502 communicates normally.

   NO:  There is no action to be taken.

5. STEP 5. Check the immobilizer-ECU ground circuit by backprobing. 
   1. Do not disconnect immobilizer-ECU connector C-128.
      Fig 7: Identifying Connector C-128

      Courtesy of DAIMLERCHRYSLER CORPORATION
   2. Measure the resistance between terminal 3 and ground by backprobing.

   Q: Is the resistance less than 2 ohm? 

   YES  : Go to  Step 8.

   NO:  Go to Step 6.

   Fig 8: Measuring Resistance Between Terminal 3 And Ground

   Courtesy of DAIMLERCHRYSLER CORPORATION
6. STEP 6. Check immobilizer-ECU connector C-128 for damage. 

   Q: Is immobilizer-ECU connector C-128 in good condition? 

   YES  : Go to Step 7.

   NO:  Repair or replace the connector. Refer to , HARNESS CONNECTOR INSPECTION . Confirm that scan tool MB991502 communicates normally.

   Fig 9: Identifying Connector C-128

   Courtesy of DAIMLERCHRYSLER CORPORATION
7. STEP 7. Check the wiring harness between immobilizer-ECU connector C-128 (terminal 3) and ground. 

   Q: Is the wiring harness between immobilizer-ECU connector C-128 (terminal 3) and ground damaged? 

   YES  : Repair the wiring harness. Confirm that scan tool MB991502 communicates normally.

   NO:  There is no action to be taken.

   Fig 10: Identifying Connector C-128

   Courtesy of DAIMLERCHRYSLER CORPORATION
8. STEP 8. Check immobilizer-ECU connector C-128 and ECM connector C-116 < 2.4L M/T >, C-122 < 3.0L M/T > or PCM connector C-121 < 2.4L A/T >, C-123 < 3.0L A/T > for damage. 

   Q: Are immobilizer-ECU connector C-128 and ECM connector C-116 < 2.4L M/T >, C-122 < 3.0L M/T > or PCM connector C-121 < 2.4L A/T >, C-123 < 3.0L A/T > in good condition? 

   YES  : Go to Step 9.

   NO:  Repair or replace the connector(s). Refer to , HARNESS CONNECTOR INSPECTION . Confirm that scan tool MB991502 communicates normally.

   Fig 11: Identifying Connectors C-116

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 12: Identifying Connector C-128

   Courtesy of DAIMLERCHRYSLER CORPORATION
9. STEP 9. Check the wiring harnesses between immobilizer-ECU connector C-128 (terminal 5) and ECM connector C-116 (terminal 51) < 2.4L M/T >, C-122 (terminal 98) < 3.0L M/T > or PCM connector C-121 (terminal 111) < 2.4L A/T >, C-123 (terminal 111) < 3.0L A/T >. 
   Fig 13: Identifying Connectors C-25, C-128

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 14: Identifying Connectors C-121, C-122

   Courtesy of DAIMLERCHRYSLER CORPORATION
   NOTE: Also check the intermediate connector C-25. If intermediate connector C-25 is damaged, repair or replace the connector. Refer to , HARNESS CONNECTOR INSPECTION .

   Q: Are the wiring harnesses between immobilizer-ECU connector C-128 (terminal 5) and ECM connector C-116 (terminal 51) < 2.4L M/T >, C-122 (terminal 98) < 3.0L M/T > or PCM connector C-121 (terminal 111) < 2.4L A/T >, C-123 (terminal 111) < 3.0L A/T > damaged? 

   YES  : Repair the wiring harness(es). Confirm that scan tool MB991502 communicates normally.

   NO:  Go to Step 10.

10. STEP 10. Replace the immobilizer-ECU. 

    Replace the immobilizer-ECU.

    Q: Did the communication with scan tool MB991502 become possible after replacing the immobilizer-ECU? 

    YES  : Register the password (secret code) and encrypted code (Refer to SPECIAL TOOLS  .) Confirm that scan tool MB991502 communicates normally.

    NO:  Go to Step 11.

11. STEP 11. Retest the system. 

    Q: Is a malfunction eliminated? 

    YES  : The procedure is complete.

    NO:  Replace the ECM < M/T > or PCM < A/T >.