Diagnosis System

1. As shown in Fig 1 , all ECUs on this vehicle are connected to each other via communication buses through which various signals are transmitted. These communication buses are diagnosed by the multiplex network body ECU.

   When the multiplex network body ECU detects a communication error between ECUs, or +B short or GND short of a communication bus, a DTC is output and stored. The multiplex network body ECU cannot diagnose accurately unless it can function normally. Therefore, first confirm the normal condition by performing the "BASIC INSPECTION" described later, and then, troubleshoot each DTC.

   Fig 1: Multiplex Communication Diagnosis System

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2. If DTC of ECU communication stop is output, connectors may be disconnected, or communication buses may be open at 2 points. It will not become abnormal with only 1 communication bus open.
   Fig 2: ECU Communication Diagram

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3. If 2 communication buses are open at the position as shown in the illustration, DTC of ECU communication stop between those 2 buses is output.
   Fig 3: Multiplex Communication System Diagram

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1. The multiplex network body ECU controls the function of the multiplex communication system of the vehicle. Data of the multiplex communication system and the Diagnostic Trouble Codes (DTC) can be read through the Data Link Connector 3 (DLC3) of the vehicle.

HINT:

The vehicle uses ISO 9141-2 communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.

Fig 4: Checking DLC3

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If the result is not as specified, the DLC3 may have a malfunction. Repair or replace the harness and connector.

HINT:

Connect the cable of the intelligent tester (with CAN VIM) to the DLC3, turn the ignition switch ON and attempt to use the tester. If the screen displays the message UNABLE TO CONNECT TO VEHICLE, there is a problem either with the vehicle or with the tester.

• If communication is normal when the tester is connected to another vehicle, inspect the DLC3 of the original vehicle.
• If communication is still not possible when the tester is connected to another vehicle, the problem may be in the tester itself. Consult the Service Department listed in the tester's instruction information.

Fig 5: Connecting Intelligent Tester To DLC3

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OK: GO TO STEP   3 

NG: GO TO NEXT STEP 

Fig 6: Checking Multiplex Network Body ECU Power Source Circuit (1 Of 2)

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Fig 7: Checking Multiplex Network Body ECU Power Source Circuit (2 Of 2)

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1. Disconnect the multiplex network body ECU connector.
2. Check voltage (terminal BECU/, BDR1/SIG and GND1/GND2).

   Standard voltage: 10 to 14 V 

3. Check the continuity (terminal GND1/GND2 and body ground.

   OK: There is a continuity between the connectors. 

4. Turn the ignition switch ON.
5. Check voltage (terminal ACC and GND1/GND 2).

   Standard voltage: 10 to 14 V 

NG: REPAIR OR REPLACE HARNESS AND CONNECTOR 

OK: GO TO NEXT STEP 

Fig 8: Checking Wire Harness (Multiplex Network Body ECU - DLC3)

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HINT:

If there is a failure in the SIL line, the intelligent tester cannot communicate with the ECM.

NG: REPAIR OR REPLACE HARNESS AND CONNECTOR 

OK: REPLACE MULTIPLEX NETWORK BODY ECU