DIAGNOSTIC ITEM 19: Diagnose When The Scan Tool (M.U.T.-IIISE) Cannot Receive The Data Sent By ACC/FCM-ECU. <Vehicles With ACC>: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe

1. STEP 1. Connector check: joint connector (CAN4) and ACC/FCM-ECU connector 
   CAUTION: The strand end of the twist wire should be within 10 cm (3.9 inches) from the connector. For details refer to TEST EQUIPMENT  .

   When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.

   Q: Is the check result normal? 

   YES:  Go to Step  2.

   NO:  Repair the defective connector. Replace the joint connector as necessary.

2. STEP 2. Resistance measurement at joint connector (CAN4) and ACC/FCM-ECU connector. 
   CAUTION: A digital multimeter should be used. For details refer to TEST EQUIPMENT  .
   CAUTION: The test wiring harness should be used. For details refer to TEST EQUIPMENT  .
   1. Disconnect joint connector (CAN4) and the ACC/FCM-ECU connector, and measure at the wiring harness side.
   2. Turn the ignition switch to the "LOCK" (OFF) position.
      CAUTION: When measuring the resistance, disconnect the negative battery terminal. For details refer to TEST EQUIPMENT  .
   3. Ensure that the negative battery terminal is disconnected.
   4. Continuity between joint connector (CAN4) terminal No. 9 and ACC/FCM-ECU connector terminal No. 6

      OK: The resistance should be 2 ohms or less 

   5. Continuity between joint connector (CAN4) terminal No. 20 and ACC/FCM-ECU connector terminal No. 1

      OK: The resistance should be 2 ohms or less 

   CAUTION: Strictly observe the specified wiring harness repair procedure. For details refer to TEST EQUIPMENT  .

   Q: Is the check result normal? 

   YES:  <All the resistances measure 2 ohms or less> Go to Step  3.

   NO:  <Either or all of the resistances measure more than 2 ohms> Repair the wiring harness between joint connector (CAN4) and the ACC/FCM-ECU connector.

3. STEP 3. Resistance measurement at ACC/FCM-ECU connector. 
   CAUTION: A digital multimeter should be used. For details refer to TEST EQUIPMENT  .
   1. Remove the ACC/FCM-ECU, and measure at the equipment side.
   2. Resistance between ACC/FCM-ECU connector terminal Nos.6 and 1

      OK: 1 kΩ or more 

   Q: Is the check result normal? 

   YES:  Power supply to the ACC/FCM-ECU may be suspected. Diagnose the ACC. Refer to SYMPTOM CHART .

   NO:  Replace the ACC/FCM-ECU.