Caution / Notice / Hint

WARNING: This page is about a different car, the 2024 Lexus LS 500h. However, it is still accessible from the selected car via links, so may be relevant.

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 [10/2017 - ]
- 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 or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
- After the ignition switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.
  Refer to BEFORE DISCONNECTING BATTERY [10/2023 - ]
- When disconnecting and reconnecting the auxiliary battery.
  Refer to WORK PROCEDURE [10/2022 - ]
  
  HINT:
  
  When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.
  
  Refer to AUTOMATIC LEARNING CHART [10/2023 - ]
- Some parts must be initialized and set when replacing or removing and installing parts.
  Refer to WORK PROCEDURE [10/2023 - ]
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 inspection can only be used to detect malfunctions in the diagnosis bus (the bus which connects the DLC3 to the central gateway ECU [network gateway ECU]).
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 GTS. (This inspection is possible when all the main bus lines are normal.)
4. In the event of communication error history in the central bus, identify the ECUs or sensors which were not communicating by analyzing the combination of stored DTCs or by performing Communication Bus Check (Detail).
5. If a sub bus has a communication error, the gateway function equipped ECU (sub bus monitor ECU) detects it and stores DTCs related to the error.
  HINT:
  
  On the GTS, gateway function equipped ECUs display DTCs for ECUs connected to the sub bus.
6. 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.
7. When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.