CAN Communication System - Diagnostics: Overview Lexus GX J120

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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 hazardous driving.
2. HANDLING PRECAUTIONS ON SRS AIRBAG SYSTEM This vehicle is equipped with an SRS (Supplemental Restraint System), such as the driver airbag and front passenger airbag. Failure to carry out service operations in the correct sequence could cause the SRS airbag to unexpectedly deploy during servicing, possibly leading to a serious accident. Before servicing (including removal or installation of parts, inspection or replacement), be sure to read the «PRECAUTION»(ref-228800-S14421764032006041100000) notice for the Supplemental Restraint System article.
3. WIRE HARNESS REPAIR After repairing the wire bus line with solder, wrap the repaired part with vinyl tape. NOTE: The CANL bus line and CANH bus line must be installed together all the time. When installing, make sure to twist them. The difference in length of the CANL bus line and CANH bus line should be within 100 mm (3.93 in.). Untwisted parts around the connector should be within 80 mm (3.15 in.). Do not use a bypass wire between the connectors. NOTE: If you use a bypass wire, the characteristic of the twisted wire harness will be lost.
4. CONNECTOR HANDLING When inserting tester probes into a connector, insert them from the back of the connector. If it is impossible to check resistance from the back of the connector, use a repair wire to check it.

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HINT

1. The skid control ECU stores DTCs and performs DTC communication by receiving information from the steering angle sensor and yaw rate sensor. These sensors cannot store DTCs or perform DTC communication.
2. The ECM uses the CAN communication system to perform DTC communication instead of the conventional serial communication line (SIL).

SYSTEM DESCRIPTION

1. BRIEF DESCRIPTION CAN (Controller Area Network) is a serial data communication system for real time application. It is an in-vehicle multiplex communication system which has a high communication speed (500 kbps) and a function to detect malfunctions. The CAN performs communication based on differential voltage by pairing the CANH bus line and CANL bus line. This vehicle uses the CAN communication system for communication between the components in the ABS with EBD & BA & TRC & VSC system. The CAN has two resistors of 120 ohm that are necessary for communication with the main bus line.
2. DEFINITION OF TERMS Main bus line The main bus line is a 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 The sub bus line is a wire harness which diverges from the main bus line to an ECU or sensor. Terminus circuit The terminus circuit is a circuit which is placed to convert communication current of the CAN communication into bus voltage. It consists of a resistor and condenser. Two terminus circuits are necessary for a bus. CAN J/C The CAN J/C is a junction designed for CAN communication, which stores a terminus circuit.
3. COMPONENTS WHICH COMMUNICATE THROUGH THE CAN COMMUNICATION SYSTEM Skid Control ECU Steering Angle Sensor Yaw Rate Sensor ECM
4. DIAGNOSTIC CODES FOR THE CAN COMMUNICATION SYSTEM DTCs for the CAN communication system are as follows: U0073/94, U0123/62, U0124/95, U0126/63, U0100/65
5. REMARKS FOR TROUBLESHOOTING Trouble in the CAN bus (communication line) can be checked from the DLC3 (except a wire break in lines other than the DLC3 sub bus line). The CAN communication system cannot detect trouble in the DLC3 sub bus line even though the DLC3 is also connected to the CAN communication system.
6. HOW TO DISTINGUISH THE J/C CONNECTOR In the CAN communication system, all connectors connected to the CAN J/C are the same shape. The connectors connected to the CAN J/C can be distinguished by the colors of the bus lines and the connecting side of the connector. HINT: See «TERMINALS OF ECU»(ref-228775-S14926384842006041100000) for bus line colors or the type of connecting surface.

See also:
• ECM (2UZ-FE)