CAN Communication System (Diagnostics - Introduction): Overview Toyota Corolla XI

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1. NOTICE FOR INITIALIZATION NOTE: When disconnecting the cable from the negative (-) battery terminal, initialize the following systems after the cable is reconnected. System See Procedure Air Conditioning System (for Automatic Air Conditioning System) Refer to «INITIALIZATION [08/2013 - ]»(ref-635429-S20696467122014070300000)
2. IGNITION SWITCH EXPRESSIONS The type of ignition switch used on this model differs depending on the specifications of the vehicle. The expressions listed in the table below are used in this article. Expression Ignition Switch (Position) Engine Switch (Condition) Ignition Switch off LOCK Off (Lock) Ignition Switch ACC ACC On (ACC) Ignition Switch ON ON On (IG) Engine Start START On (Start)
3. CAN COMMUNICATION SYSTEM TROUBLESHOOTING 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. Refer to «HOW TO PROCEED WITH TROUBLESHOOTING [08/2013 - ]»(ref-635647-S27781195552014070300000)
4. PRECAUTION FOR STEERING SYSTEM HANDLING Be careful when replacing parts. Incorrect replacement could affect the performance of the steering system and result in hazardous driving.
5. PRECAUTION 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 Precaution for SRS. Refer to «PRECAUTION [08/2013 - 04/2014]»(ref-635668-S07633225772014070300000) & «PRECAUTION [04/2014 - ]»(ref-635668-S18447933222014070300000)
6. BUS LINE REPAIR After repairing a bus line with solder, wrap the repaired part with electrical tape. NOTE: The CANL bus line and CANH bus line must be installed together at all times. When installing, make sure that these lines are twisted, because CAN bus lines are likely to be influenced by electrical noise if the bus lines are not twisted. Leave approximately 80 mm (3.15 in.) loose in the twisted wires around the connector. When repairing the CAN bus lines, do not change the length of the lines. (Make sure that the length of the CANH bus line and CANL bus line are the same.) Do not use bypass wiring between connectors. *a Bypass Wire NOTE: The ability of the twisted bus lines to resist interference will be lost if bypass wiring is used. Do not use a twisted pair of wires for bypass wiring.
7. CONNECTOR HANDLING When checking resistance with a tester, insert the tester probes from the backside (harness side) of the connector. *a Tester Probe Use service wires to check the connector if it is impossible to check continuity from the rear of the connector. *a Service Wire

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SYSTEM DESCRIPTION [04/2014 - ]

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. Using the CANH and CANL bus lines as a pair, CAN communication is performed using a voltage differential. (A base voltage is applied to the pair of lines and a voltage differential is created when communicating.) 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 enable communication.
2. DEFINITION OF TERMS Main bus The main bus is a wire harness between the two terminating resistors on the bus. This is the main bus in the CAN communication system. Branch A branch is a wire harness which diverges from the main bus to an ECU or sensor. Terminating resistors Two resistors of 120 ohms are installed in parallel across the ends of the CAN main bus lines. They are called terminating resistors. These resistors allow the changes of the voltage differential between the CAN bus lines to be accurately judged. To allow proper function of CAN communication, it is necessary to have both terminating resistors installed. Since the two resistors are installed in parallel, this results in a measurement of approximately 60 ohms.
3. ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM V Bus Combination meter assembly Certification ECU (smart key ECU assembly)*1 Navigation receiver assembly*2 Radio and display receiver assembly*3 Airbag sensor assembly Power steering ECU assembly Air conditioning amplifier assembly*4 Skid control ECU (brake actuator assembly) Steering sensor*5 Main body ECU (multiplex network body ECU) ECM HINT: *1: w/ Smart Key System *2: for Navigation Receiver Type *3: for Radio and Display Type *4: w/ Air Conditioning System *5: w/ VSC
4. CIRCUIT DESCRIPTION The V bus has termination circuits with two resistors of 120 ohms.
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 lines. If there is a malfunction in the DLC3 or the DLC3 branch lines, ECUs on the CAN cannot output DTCs to the Techstream. Malfunctions in the CAN V bus (communication lines) can be checked by measuring the resistance between terminals of the DLC3. However, an open circuit in a branch line other than the DLC3 branch lines cannot be checked from the DLC3 (except for the DLC3 branch lines). NOTE: Do not insert the tester probes directly into the DLC3. Be sure to use service wires.
6. DIAGNOSTIC TROUBLE CODES FOR CAN COMMUNICATION SYSTEM HINT: See Diagnosis System. Refer to «DIAGNOSIS SYSTEM [04/2014 - ]»(ref-635652-S02842089492014070300000)
7. 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 are the same. The connectors connected to the CAN junction connector can be distinguished by the colors of the bus lines and the connecting side of the junction connector. HINT: See Terminals of ECU for bus line color or the shape of connecting surface. Refer to «TERMINALS OF ECU [04/2014 - ]»(ref-635647-S42134172692014070300000)