Diagnosis Procedure

Required Special Tools: 

• MB991223: Harness Set
• MB991958: Scan Tool (MUT-III Sub Assembly)
  • MB991824: Vehicles Communication Interface (V.C.I.)
  • MB991827: MUT-III USB Cable
  • MB991910: Main Harness A

1. STEP 1. Check if scan tool MB991958 can communicate with the MFI system and if an MFI system DTC other than P0513 is set. 

   Q: Can scan tool MB991958 communicate with the MFI system? Is an MFI system DTC other than P0513 set? 

   1. YES  : Go to Step 2.
   2. NO  : Refer to DIAGNOSIS .
   Fig 1: Connecting Scan Tool To Data Link Connector

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2. STEP 2. Check the immobilizer-ECU power supply circuit by backprobing. 
   1. Do not disconnect immobilizer-ECU connector C-113.
   2. Turn the ignition switch to the "ON" position.
      Fig 2: Identifying Immobilizer-ECU Connector C-113

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   3. Measure the voltage between terminal 1 and ground by backprobing.
      • The voltage should measure approximately 12 volts (battery positive voltage).

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

   1. YES  : Go to  Step 5.
   2. NO  : Go to Step 3.
   Fig 3: Measuring Voltage Between Terminal 1 And Ground

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3. STEP 3. Check immobilizer-ECU connector C-113 and MFI relay connector B-16X for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Are immobilizer-ECU connector C-113 and MFI relay connector B-16X in good condition? 

   1. YES  : Go to Step 4.
   2. NO  : Repair or replace the component(s). Refer to HARNESS CONNECTOR INSPECTION . Confirm that scan tool MB991958 communicates normally.
   Fig 4: Identifying MFI Relay Connector B-16X

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   Fig 5: Identifying Immobilizer-ECU Connector C-113

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4. STEP 4. Check the harness wires between immobilizer-ECU connector C-113 (terminal 1) and MFI relay connector B-16X (terminal 1). 
   Fig 6: Identifying MFI Relay Connector B-16X

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   Fig 7: Identifying Immobilizer-ECU Connector C-113

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   NOTE: Also check intermediate connector C-117, C-106 and joint connector C-17, check the wires. If intermediate connector C-117, C-106 and joint connector C-17 are damaged, repair or replace them. Refer to HARNESS CONNECTOR INSPECTION .

   Q: Are the harness wires between immobilizer-ECU connector C-113 (terminal 1) and MFI relay connector B-16X (terminal 1) in good condition? 

   1. YES  : There is no action to be taken.
   2. NO  : Repair the component(s). Confirm that scan tool MB991958 communicates normally.
   Fig 8: Identifying Connector Terminals C-17 And C-106

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   Fig 9: Identifying Connector Terminals C-117

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5. STEP 5. Measure the resistance at immobilizer-ECU connector C-113. 
   1. Do not disconnect immobilizer-ECU connector C-113.
      Fig 10: Identifying Immobilizer-ECU Connector C-113

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   2. Measure the resistance between terminal 2 and ground.

   Q: Is the resistance less than 2 ohms? 

   1. YES  : Go to  Step 8.
   2. NO  : Go to Step 6.
   Fig 11: Measuring Resistance Between Terminal 2 And Ground

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6. STEP 6. Check immobilizer-ECU connector C-113 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is immobilizer-ECU connector C-113 in good condition? 

   1. YES  : Go to Step 7.
   2. NO  : Repair or replace the damaged component(s). Refer to HARNESS CONNECTOR INSPECTION . Confirm that scan tool MB991958 communicates normally.
   Fig 12: Identifying Immobilizer-ECU Connector C-113

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7. STEP 7. Check the harness wires between immobilizer-ECU connector C-113 (terminal 2) and ground. 

   Q: Is the harness wire between immobilizer-ECU connector C-113 (terminal 2) and ground in good condition? 

   1. YES  : There is no action to be taken.
   2. NO  : Repair the harness wire. Confirm that scan tool MB991958 communicates normally.
   Fig 13: Identifying Immobilizer-ECU Connector C-113

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8. STEP 8. Check immobilizer-ECU connector C-113 and ECM < M/T > or PCM < A/T > connector C-111 for loose, corroded or damaged terminals, or terminal pushed back in the connector. 

   Q: Is immobilizer-ECU connector C-113 and ECM < M/T > or PCM < A/T > connector C-111 in good condition? 

   1. YES  : Go to Step 9.
   2. NO  : Repair or replace the damaged component(s). Refer to HARNESS CONNECTOR INSPECTION . Confirm that scan tool MB991958 communicates normally.
   Fig 14: Identifying Connector Terminals C-111 And C-113

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9. STEP 9. Check the harness wires between immobilizer-ECU connector C-113 and ECM < M/T > or PCM < A/T > connector C-111. 
   NOTE: Also check intermediate connector C-104, check the wires. If intermediate connector C-104 are damaged, repair or replace them. Refer to HARNESS CONNECTOR INSPECTION .

   Q: Are the harness wires between immobilizer-ECU connector C-113 and PCM connector C-111 in good condition? 

   1. YES  : Go to Step 10.
   2. NO  : Repair the harness wire. Confirm that scan tool MB991958 communicates normally.
   Fig 15: Identifying Connector Terminals C-104, C-111 And C-113

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10. STEP 10. Replace the immobilizer-ECU, ECM < M/T > or PCM < A/T >. 

    Replace the immobilizer-ECU, ECM < M/T > or PCM < A/T >.

    Q: Did the communication with the scan tool become possible after replacing the immobilizer-ECU, the ECM < M/T > or PCM < A/T >? 

    1. YES  : Register the password (secret code) and encrypted code HOW TO REGISTER ENCRYPTED CODE . Confirm that scan tool MB991958 communicates normally
    2. NO  : Go to Step 11.
11. STEP 11. Recheck for malfunction. 

    Q: Is a malfunction eliminated? 

    1. YES  : The procedure is complete (If no malfunction are found in all steps, an intermittent malfunction is suspected. Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
    2. NO  : Replace the immobilizer-ECU or ECM < M/T > or PCM < A/T >. Then register the password (secret code) and encrypted code (Refer to HOW TO REGISTER ENCRYPTED CODE ).