CAN Communication (Diagnostics - Introduction): Overview Lexus GS III facelift

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1. STEERING SYSTEM HANDLING PRECAUTIONS Care must be taken when replacing parts. Incorrect replacement could affect the performance of the steering system and result in hazardous driving.
2. SRS AIRBAG SYSTEM HANDLING PRECAUTIONS 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 unexpected SRS deployment during servicing and may lead to a serious accident. Before servicing (including installation/removal, inspection and replacement of parts), be sure to read the precautionary notice for the Supplemental Restraint System. Refer to «PRECAUTION»(ref-382572-S21349992902011012800000) .
3. BUS LINE REPAIR After repairing the 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 the CAN bus lines, make sure to twist them. CAN bus lines are likely to be influenced by noise if the bus lines are not twisted. The difference in length of the CANL bus line and CANH bus line should be within 100 mm (3.937 in.). Leave approximately 80 mm (3.150 in.) loose in the twist around the connector. Do not use bypass wiring between the connectors. NOTE: The feature of the twisted wire harness will be lost if using bypass wiring.
4. CONNECTOR HANDLING When inserting tester probes into a connector, insert them from the rear of the connector. Use a repair wire to check the connector if it is impossible to check continuity from the rear of the connector.
5. PRECAUTION FOR DISCONNECTING THE BATTERY CABLE NOTE: When disconnecting the negative (-) battery terminal, initialize the following system after the terminal is reconnected. System Name See Procedure Power Window Control System Refer to «INITIALIZATION»(ref-382578-S40254115562011012800000) Intuitive Parking Assist System Variable Gear Ratio Steering System Perform the RESET MEMORY (AT initialization) operation after replacing the automatic transmission assembly, engine assembly or ECM. HINT: RESET MEMORY cannot be completed by only disconnection of the battery terminal.

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HINT

1. The skid control ECU detects and stores steering sensor and yaw rate sensor DTCs and performs DTC communication by receiving information from the steering sensor and yaw rate sensor.
2. The ECM detects and stores distance control ECU DTCs, and performs DTC communication by receiving information from the distance control ECU.

SYSTEM DESCRIPTION

1. BRIEF DESCRIPTION The CAN (Control Area Network) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed (500 kbps) and the ability to detect malfunctions. By pairing the CANH and CANL bus lines, the CAN perform communication based on differential voltage. Many ECUs (sensors) installed on the vehicle operate by sharing information and communicating with each other. The CAN has two resistors of 120 ohms which are necessary to communicate 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 converts communication current of the CAN communication into bus voltage. It consists of a resistor and a condenser. Two terminus circuits are necessary on a bus. CAN J/C The CAN J/C is designed so that it can be used with CAN communication which has termination circuits and CAN communication which does not have termination circuits.
3. CIRCUIT DESCRIPTION The CAN communication system consists of the CAN No. 1 bus and CAN No. 2 bus circuits, which are connected through the gateway CAN ECU. The CAN No. 1 bus and CAN No. 2 bus each have termination circuits with 120 ohms of resistance. High speed communication at 500 kbps is possible.
4. ECUs OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM Skid control ECU Yaw rate sensor Steering angle sensor Seat belt control ECU Distance control ECU Absorber control ECU ECM Network gateway ECU Clearance warning ECU Power steering ECU Steering control ECU 4WD ECU Gateway CAN ECU Front active stabilizer control ECU Rear active stabilizer control ECU
5. DIAGNOSTIC CODE FOR CAN COMMUNICATION SYSTEM DTCs for the CAN communication system are as follows: U0073, U0100, U0101, U0104, U0114, U0122, U0123, U0124, U0126, U0130, U0131, U0132, U0145, U0146, U1002, U1101, U1108, U1109 and U1110.
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). NOTE: Do not insert the tester directly into the DLC3 connector. Be sure to use a service wire. DTCs reading the CAN communication system can be checked using the Techstream via the CAN VIM. The CAN communication system cannot detect trouble in the sub bus line of the DLC3 even though the DLC3 is also connected to the CAN communication system.
7. HOW TO DISTINGUISH THE CAN J/C CONNECTOR In the CAN communication system, the shape of all connectors connected to the CAN J/C is the same. The connectors connected to the CAN J/C can be distinguished by the colors of the bus line and the connecting side of the connector. HINT: See "TERMINALS OF ECU" . Refer to «TERMINALS OF ECU»(ref-382784-S00438423332011012800000) for bus line color or the type of connecting surface.