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Home >> Toyota >> 2014 >> Corolla L, Automatic Trans >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Communication Devices >> Can Communication System - (W/O Central Gateway Ecu) - Diagnostics - Introduction (1 Of 2) (Model Code: ZRE172) >> CAN COMMUNICATION SYSTEM (W/O Central Gateway ECU) >> How To Proceed With Troubleshooting [08/2013 - ] >> Caution / Notice / Hint
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Caution / Notice / Hint

  1. PRECAUTIONS WHEN TROUBLESHOOTING 
    NOTE:
    • Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
    • If the CAN communication system is malfunctioning, check the contact pressure of the terminals in connectors, as insufficient terminal contact pressure may be the cause.

      Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [08/2013 - ]

    • Refer to Diagnosis System for CAN communication system DTCs.
    • Refer to troubleshooting of each system if DTCs regarding the CAN communication system are not output.
    • Before measuring the resistance of the CAN bus, turn the ignition switch off and leave the vehicle for 1 minute or more without operating the key, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
    • After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

      Refer to PRECAUTION [08/2013 - 08/2015] Refer to PRECAUTION [08/2015 - 08/2016] Refer to PRECAUTION [08/2016 - ]

    1. CAN communication DTCs are output for CAN main bus and CAN branch malfunctions as well as for internal malfunctions or power source malfunctions of ECUs or sensors for systems using CAN communication. Therefore, when DTCs for internal malfunctions or power source malfunctions of corresponding systems are output at the same time as CAN communication DTCs, troubleshoot according to the internal malfunction and power source malfunction DTCs.
    2. The DLC3 branch and V bus main bus circuits can be checked for malfunctions by inspecting at the DLC3 terminals using an electrical tester.
      NOTE:
      • When inspecting at the DLC3 connector, do not connect the tester directly to the terminals. Instead, connect using service wires.
      • Inspections for an open in an ECU or sensor branch, or inspections for buses other than the V bus cannot be performed from the DLC3.
    3. An open in a branch for ECUs or sensors that are connected to the CAN main bus can be checked by performing a CAN bus check using the Techstream. (This inspection is possible when the DLC3 branch and V bus main bus lines are normal.)
    4. If the V bus had a communication error, the probable ECU or sensor for which communication stopped can be determined using the combination of communication DTCs (DTCs that start with U) that are output.
    5. When an open circuit is detected, before disconnecting related connectors for inspection, push in on the connector body to check that the connector is not loose or disconnected.
    6. When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.
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