CAN Communication System (Diagnostics - Introduction): Overview Lexus HS I

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1. PRECAUTIONS FOR STEERING SYSTEM HANDLING Be careful when replacing parts. Incorrect replacement could affect the performance of the steering system and result in hazardous driving.
2. PRECAUTIONS FOR SRS AIRBAG SYSTEM HANDLING This vehicle is equipped with a Supplemental Restraint System (SRS) which includes parts such as airbags for the driver and front passenger. Failure to carry out service operations in the correct sequence could cause unexpected SRS deployment during servicing and may cause a serious accident. Before servicing (including removal or installation of parts, inspection or replacement), be sure to read the precaution for the SRS. Refer to «PRECAUTION»(ref-398246-S19065826952011051600000) .
3. BUS WIRE REPAIR After repairing a bus wire with solder, wrap the repaired part with electrical tape. NOTE: The CANL bus wire and CANH bus wire must be installed together at all times. When installing, make sure that these wires are twisted, because CAN bus wires are likely to be influenced by electrical noise if the bus wires are not twisted. The difference in length between the CANL bus wire and CANH bus wire should be 100 mm (3.937 in.) or less. Leave approximately 80 mm (3.150 in.) loose in the twisted wires around the connector. Do not use bypass wiring between connectors. NOTE: The ability of the twisted bus wires to resist interference will be lost if bypass wiring is used.
4. CONNECTOR HANDLING When checking resistance with a tester, insert the tester probes from the backside (harness side) of the connector. Use service wires to check the connector if it is impossible to check continuity from the rear of the connector.
5. PRECAUTIONS FOR INSPECTING OR REPLACING CAN JUNCTION CONNECTOR If the CAN junction connector is removed from the vehicle for inspection or replacement, make sure to install the CAN junction connector and all wire harnesses to their original locations with tape and the clamps.

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1. CAN No. 1 BUS
2. CAN No. 2 BUS
3. CAN MS BUS
4. POWER MANAGEMENT BUS
5. DRIVING SUPPORT BUS (w/ Dynamic Radar Cruise Control System)

SYSTEM DESCRIPTION

1. BRIEF DESCRIPTION The Controller Area Network (CAN) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed and the ability to detect malfunctions. By pairing the CANH and CANL bus wires, the CAN performs communication based on differential voltage. Many ECUs or 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 wire.
2. DEFINITION OF TERMS Main bus wire The main bus wire is a wire harness between the two terminating resistors on the bus (communication wire). This is the main bus in the CAN communication system. Branch wire The branch wire is a wire harness which diverges from the main bus wire to an ECU or sensor. Terminating resistors The termination circuit is a circuit which converts the communication current of CAN communication into the bus voltage. It consists of a resistor and condenser. Two termination circuits are necessary on the bus.
3. ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM CAN No. 1 Bus Hybrid vehicle control ECU Power management control ECU Transmission control ECU Brake booster with master cylinder (Skid control ECU) Airbag sensor assembly Multiplex network body ECU (Main body ECU) Smart key ECU (Certification ECU) Combination meter Display and navigation module display (Navigation ECU)*1 Headlight swivel ECU (AFS ECU)*2 Driving support ECU*3 Seat belt control ECU*4 CAN No. 2 Bus Power management control ECU Hybrid vehicle control ECU Brake booster with master cylinder (Skid control ECU) Power steering ECU Spiral cable with sensor (Steering angle sensor) Yaw rate sensor Parking assist ECU*5 Clearance warning ECU*6 CAN MS Bus Multiplex network body ECU (Main body ECU) Tire pressure monitor ECU Multiplex tilt and telescopic ECU*7 Front power seat switch LH*7 Outer mirror control ECU LH*7 Outer mirror control ECU RH*7 Power Management Bus Power management control ECU Air conditioning amplifier Driving Support Bus*3 Driving support ECU Millimeter wave radar sensor Lane recognition camera sensor*8 Driver monitor ECU*9 HINT: *1: w/ Navigation system *2: w/ AFS *3: w/ Dynamic radar cruise control system *4: w/ Pre-collision system *5: w/ Wide view front monitor system *6: w/ Intuitive parking assist system *7: w/ Seat position memory *8: w/ Lane-keeping assist system *9: w/ Driver monitor system
4. CIRCUIT DESCRIPTION The CAN No. 1 bus, CAN No. 2 bus, power management bus, CAN MS bus and driving support bus each have termination circuits with two resistors of 120 ohms. High speed communication at 500 kbps is possible.
5. TROUBLESHOOTING REMARKS DTCs for the CAN communication system can be checked using the Techstream. The DLC3 is connected to the CAN communication system, but no DTCs exist regarding problems in the DLC3 or the DLC3 branch wires. If there is any trouble in the DLC3 or the DLC3 branch wires, ECUs on the CAN network cannot output codes to the Techstream. Trouble in the CAN buses (communication wires) can be checked by measuring the resistance between terminals of the DLC3. However, an open circuit in a branch wire other than the DLC3 branch wires cannot be checked from the DLC3. NOTE: Do not insert the tester probes directly into the DLC3. Be sure to use service wires.
6. DIAGNOSTIC TROUBLE CODE FOR CAN COMMUNICATION SYSTEM HINT: See Diagnosis System. Refer to «DIAGNOSIS SYSTEM»(ref-398235-S15853483682011051600000) .
7. NOTES REGARDING TROUBLESHOOTING Trouble in the CAN bus (communication line) can be checked through the DLC3 (except when there is a wire break other than in the branch wire of the DLC3). NOTE: Do not insert the tester probes directly into the DLC3. Be sure to use service wires. DTCs regarding the CAN communication system can be checked using the Techstream. The CAN communication system cannot detect trouble in the branch wires for the DLC3 even though the DLC3 is also connected to the CAN communication system.
8. HOW TO DISTINGUISH CONNECTOR OF CAN JUNCTION CONNECTOR In the CAN communication system, the shape of connectors connected to the CAN junction connector which has an earth terminal is the same. The connectors connected to the CAN junction connector can be distinguished by the colors of the bus wires and the connecting side of the junction connector. HINT: See Terminals of ECU for bus wire color or the shape of connecting surface. Refer to «TERMINALS OF ECU»(ref-398235-S10384021252011051600000) .