CAN Communication System - Diagnosis: Overview Lexus RX II

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1. HANDLING PRECAUTIONS ON STEERING SYSTEM Care must be taken when replacing parts. Incorrect replacement could affect the performance of the steering system and result in a driving hazard.
2. HANDLING PRECAUTIONS ON SRS AIRBAG SYSTEM The LEXUS RX330 is equipped with the SRS (Supplemental Restraint System) such as the driver's airbag and front passenger airbag. Failure to carry out service operation in correct sequence could cause unexpected SRS deployment during servicing and may lead to a serious accident. Before servicing (including removal or installation of parts, inspection or replacement), be sure to read the precautionary notice for the supplemental restraint system (See «AIR BAG SAFETY PRECAUTIONS» ).
3. BUS LINE REPAIR After repairing bus line with solder, wrap the repaired part with vinyl tape (See «ELECTRONIC CIRCUIT INSPECTION PROCEDURE» ). NOTE: The CANL bus line and CANH bus line must be installed together all the time. When installing, make sure to twist them. CAN bus lines is likely to be influenced by the noise if the bus lines are not twisted. The difference in the length of the CANL bus line and CANH bus line should be within 100 mm (3.937 in.). Leave about 80 mm (3.150 in.) loose in the twist around the connector. Do not use bypass wiring between the connectors. NOTE: If you use bypass wiring, the feature of the twisted wire harness will be lost.
4. CONNECTOR HANDLING When inserting tester probes into a connector, insert them from the rear of the connector. If it is impossible to check continuity from the rear of the connector, use a repair wire to check it.
5. HOW TO DISTINGUISH THE CAN J/C CONNECTORS CAN J/C connectors can be distinguished by the color of the bus branch lines and the location of the connectors. HINT: Refer to TERMINALS OF ECU on «TERMINALS OF ECU» for the line colors and the location of the connector.
6. When disconnecting the negative (-) battery terminal, initialize the following systems after the terminal is reconnected. INITIALIZING SYSTEMS System Refer To Lighting System (Adaptive Front-Lighting System) «PRE-CHECK» Power Window Control System «PRE-CHECK» Power Back Door System «PRE-CHECK» Sliding Roof System «PRE-CHECK»

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1. BRIEF DESCRIPTION The CAN (Controller Area Network) is a serial data communication system for real time application. It is a multiplex communication system equipped for a vehicle and has a high communication speed (500 kbps) and the function to detect malfunctions. By pairing the CANH and CANL bus lines, the CAN performs communication based on differential voltage. The RX330 uses CAN communication system for the communication between the ECU and sensors in the ABS with EBD & BA & TRAC & VSC system. The CAN has two resistors of 120 ohm's which are necessary to communicate with the main bus line.
2. DEFINITION OF TERMS Main bus line Main bus line is the wire harness between the two terminus circuits on the bus (communication line). This is the main bus in the CAN communication system. Sub bus line Sub bus line is the wire harness which diverges from the main bus line to the ECU or sensor. Terminus circuit Terminus circuit is a circuit which is placed to convert communication current of the CAN communication into bus voltage and it consists of a resistor and condenser. Two terminus circuits are necessary on a bus. CAN J/C CAN J/C is a junction which is designed for the CAN communication system, and it has a terminus circuit built in.
3. ECU OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM Skid Control ECU with Actuator (VSC ECU) Yaw Rate Sensor (with Deceleration Sensor) Steering Sensor
4. DIAGNOSTIC CODE FOR CAN COMMUNICATION SYSTEM DTCs for CAN system are as follows: U0121/94, U0123/62, U0124/95, U0126/63
5. CAN COMMUNICATION SYSTEM WIRING DIAGRAM HINT: The Skid Control ECU stores DTCs and performs DTC communication by receiving information from the Steering Sensor and Yaw Rate Sensor because these sensors cannot store DTCs or perform DTC communication.
6. REMARK FOR TROUBLESHOOTING Trouble in the CAN bus (communication line) can be checked from the DLC3 (except when there is a wire break other than in the sub bus line of the DLC3). By using the hand-held tester, DTCs for the CAN communication can be checked through the DTC ISO 9141K-Line. CAN communication cannot detect the trouble on sub bus line of the DLC3 even though the DLC3 is also connected to CAN communication.

See also:
• REPLACEMENT
• REPLACEMENT
• REPLACEMENT