CAN Communication System (Diagnostics & Symptom Tests): Overview Scion FR-S I

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1. CAN COMMUNICATION SYSTEM TROUBLESHOOTING Because the order of diagnosis is important to allow a 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 [07/2013 - 12/2013]»(ref-612381-S39654712422014042900000).
2. 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.
3. 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 the 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 [07/2013 - 12/2013]»(ref-612421-S13613575682014042900000).
4. 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 (3.150 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. TEXT IN ILLUSTRATION *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.
5. CONNECTOR HANDLING When checking resistance with a tester, insert the tester probes from the backside (harness side) of the connector. TEXT IN ILLUSTRATION *a Tester Probe Use service wires to check the connector if it is impossible to check continuity from the rear of the connector. TEXT IN ILLUSTRATION *a Service Wire
6. 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.

SYSTEM DESCRIPTION [12/2013 - ]

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. Control system CAN is composed of 1 bus.
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 The 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 Main body ECU (network gateway ECU) Combination meter assembly Certification ECU (smart key ECU assembly)*1 ECM TCM*2 Skid control ECU (brake actuator assembly) Steering angle sensor (spiral cable sub-assembly) Power steering ECU assembly Air conditioning control assembly*3 Airbag ECU assembly *1: w/ Smart Key System *2: for Automatic Transmission System *3: for Automatic Air Conditioning System
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 any trouble in the DLC3 or the DLC3 branch lines, ECUs on the CAN cannot output DTCs to the Techstream. Troubles in the CAN V bus (communication lines) can be checked by measuring the resistance between the 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 branch line of the DLC3). 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 [12/2013 - ]»(ref-612381-S29831877552014042900000).
7. HOW TO DISTINGUISH CONNECTOR OF CAN JUNCTION CONNECTOR In the CAN communication system, the shape of the 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 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 [12/2013 - ]»(ref-612381-S16788908332014042900000).

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1. PRECAUTIONS WHEN TROUBLESHOOTING NOTE: 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. If the CAN communication system is malfunctioning, check the contact pressure of the terminals in connectors, as insufficient terminal contact pressure may be the cause. Refer to «ELECTRONIC CIRCUIT INSPECTION PROCEDURE [07/2013 - ]»(ref-612229-S26482874422014042900000). Refer to Diagnosis System for the DTCs for the CAN communication system. Refer to troubleshooting of each system if DTCs regarding the CAN communication system are not output. Before measuring the resistance of the CAN bus, turn the ignition switch off and leave the vehicle for 1 minute or more without operating the key, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance. After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work. Refer to «PRECAUTION [07/2013 - ]»(ref-612229-S41967653852014042900000). CAN communication DTCs are output for CAN main bus and CAN branch malfunctions as well as for internal malfunctions or power source malfunctions of ECUs or sensors for systems using CAN communication. Therefore, when DTCs for internal malfunctions or power source malfunctions of corresponding systems are output at the same time as CAN communication DTCs, troubleshoot according to the internal malfunction and power source malfunction DTCs. The DLC3 branch and V bus main bus circuits can be checked for malfunctions by inspecting at the DLC3 terminals using an electrical tester. NOTE: When inspecting at the DLC3 connector, do not connect the tester directly to the terminals. Instead, connect using service wires. Inspections for an open in an ECU or sensor branch, or inspections for buses other than the V bus cannot be performed from the DLC3. An open in a branch for ECUs or sensors that are connected to the CAN main bus can be checked by performing a CAN bus check using the Techstream. (This inspection is possible when the DLC3 branch and V bus main bus lines are normal.) If the V bus had a communication error, the probable ECU or sensor for which communication stopped can be determined using the combination of communication DTCs (DTCs that start with U) that are output. When an open circuit is detected, before disconnecting the related connectors for inspection, push in on the connector body to check that the connector is not loose or disconnected. When a connector is disconnected, check that the terminals and the connector body are not cracked, deformed or corroded. VEHICLE BROUGHT TO WORKSHOP HINT: If the ignition switch can be turned to ON when the vehicle is brought in for repair, check for DTCs and check the illumination condition of the indicators in the combination meter assembly and the basic operation of the vehicle (such as steering operation) promptly. Do not turn the ignition switch off until the inspection of the vehicle is finished, as some fail-safe functions are canceled when the ignition switch is turned off. If the ignition switch cannot be turned to ON when the vehicle is brought in, measure the voltage of the battery. If the voltage is below 11 V, recharge or replace the battery before performing troubleshooting. NEXT: Go to next step CUSTOMER PROBLEM ANALYSIS HINT: When troubleshooting, confirm that the problem symptoms have been accurately identified. Preconceptions should be discarded in order to make an accurate judgment. To clearly understand what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time the malfunction occurred. Ask the customer if the vehicle is/was equipped with additional devices such as a theft deterrent device or monitor. (If equipped, explain the customer that the additional devices will be removed before performing troubleshooting as the malfunction cannot be checked properly.) It is useful to confirm the symptoms and the conditions in which the vehicle was operating at the time when a malfunction occurred. This helps to narrow down the malfunctioning part. HINT: What was affected (system, part or meter warning indicators) What happened (details of the malfunction) When (occurrence date and time, frequency and if it recurs or not) Under what kind of situation did the problem occur (driving and operating condition at the occurrence and weather) Road type or condition (city, suburb, paved road, unpaved road, highway, etc.) Return conditions (what made the vehicle return to normal. Example: ignition switch was turned off) POINTS TO BE CONFIRMED Symptom Electric power steering - Normal - A little heavier than usual - There was no assist Multi-information display - Whether each display has stopped updating Others Meter warning lights Illumination of warning lights and the order in which they illuminated - Slip indicator light - ABS warning light - Check Engine warning light - Brake warning light - SRS warning light - Others Meter display - Shift indicator - Speedometer - Tachometer (if it is fixed at 0 rpm) - Engine coolant temperature gauge (if it is fixed at COLD) NEXT: Go to next step CHECK TECHSTREAM OPERATION HINT: Read the Techstream operators manual before use. Refer to «GENERAL INFORMATION [07/2013 - ]»(ref-612229-S35930398492014042900000). Connect the Techstream to the DLC3. Turn the ignition switch to ON. Turn the Techstream on. Check that the Techstream and ECUs can communicate with the ignition switch ON. HINT: If communication is impossible, the Techstream screen will indicate an error. If communication between the Techstream and ECUs is impossible, either the Techstream or vehicle has a malfunction. When communication between the Techstream and the vehicle is impossible, but communication is possible when the Techstream is connected to another vehicle, the vehicle has the malfunction. Inspect the CANH and CANL branch lines of the DLC3 and the ECU power source circuits (in this case perform steps 7 to 9 first). In addition, check that the BAT terminal of the DLC3 receives battery voltage (11 V or more). If communication between the Techstream and ECUs is still impossible even when the Techstream is connected to another vehicle, the Techstream has a malfunction. Perform the self tests described in the Techstream operators manual. (The Techstream may be malfunctioning or its battery may be discharged.) Result Proceed to OK (Communication between the Techstream and the vehicle is possible.) A OK (Communication between the Techstream and the vehicle is impossible but communication is possible when connected to another vehicle.) B NG (Communication is not possible between the Techstream and the vehicle, nor between the Techstream and another vehicle.) C B --> Go to step 7 C --> Refer to Techstream operator's manual A: Go to next step CHECK DTC Using the Techstream, perform Health Check to read current and history DTCs and record them. NOTE: CAN communication DTCs are output when there is an open or short in any of the communication lines. Any problems with the power source of a corresponding ECU or sensor, or problems in the ECU, the sensor itself also cause these DTCs to be output. If a CAN communication line connector is disconnected with the ignition switch ON, the ECUs of the corresponding system and related systems store a DTC. HINT: If an open in a CAN main bus line, a short between the CAN bus lines (CANH and CANL) or a +B or ground short in a CAN bus occurs, DTCs of almost all ECUs and sensors on the CAN bus may be output (or a message indicating a communication error may be displayed on the Techstream screen). In this case, check the resistance of the CAN bus (steps 7 to 9) first. If an open occurs in just one of the lines of a CAN branch, DTCs which are not related to malfunctioning parts may be output (DTCs may be displayed randomly), or a message indicating a communication error may be displayed on the Techstream. Read the freeze frame data using the Techstream and record it. NEXT: Go to next step CHECK COMMUNICATION MALFUNCTION CHECK (CONNECTION STATUS CHECK USING TECHSTREAM) Select "CAN Bus Check" from the screen on the Techstream. Record all the DTCs stored for ECUs and sensors. NEXT: Go to next step CHECK CAN BUS CHECK (CONNECTION STATUS CHECK USING TECHSTREAM) Based on the vehicle equipment and specifications, confirm the systems that use CAN communication. Refer to «DIAGNOSIS SYSTEM [07/2013 - 12/2013]»(ref-612381-S33318737382014042900000). Select "CAN Bus Check" from the screen on the Techstream. Observe the screen for approximately 2 minutes to check the ECUs and sensors displayed on the screen. NEXT: Go to next step CHECK DLC3 BRANCH LINE AND V BUS MAIN LINE (CANH - CANL) NOTE: Before measuring the resistance of the CAN bus, turn the ignition switch off and leave the vehicle for 1 minute or more without operating the key, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance. HINT: Operating the ignition switch, any other switches or a door triggers the related ECU and sensor communication on the CAN. This communication will cause the resistance value to change. Disconnect the cable from the negative (-) battery terminal. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition D10-6 (CANH) - D10-14 (CANL) Cable disconnected from negative (-) battery terminal 57 to 63 ohms TEXT IN ILLUSTRATION *1 DLC3 Result Result Proceed to OK A NG (64 ohms or higher) B NG (Below 57 ohms) C B --> GO TO OPEN IN CAN MAIN BUS LINE. Refer to «Open in CAN Main Bus Line»(ref-612381-S21147177182014042900000) C --> GO TO SHORT IN CAN BUS LINES. Refer to «Check CAN Bus Lines for Short Circuit»(ref-612381-S39411157162014042900000) A: Go to next step CHECK FOR SHORT TO GND IN V BUS (CANH, CANL - CG) Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition D10-6 (CANH) - D10-4 (CG) Cable disconnected from negative (-) battery terminal 200 ohms or higher D10-14 (CANL) - D10-4 (CG) Cable disconnected from negative (-) battery terminal 200 ohms or higher TEXT IN ILLUSTRATION *1 DLC3 NG --> GO TO SHORT TO GND IN CAN BUS LINE. Refer to «Check CAN Bus Line for Short to GND»(ref-612381-S12911166602014042900000) OK: Go to next step CHECK FOR SHORT TO +B IN V BUS (CANH, CANL - BAT) Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition D10-6 (CANH) - D10-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kohms or higher D10-14 (CANL) - D10-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kohms or higher TEXT IN ILLUSTRATION *1 DLC3 NG --> GO TO SHORT TO +B IN CAN BUS LINE. Refer to «Check CAN Bus Line for Short to +B»(ref-612381-S04888706862014042900000) OK: Go to next step CHECK RESULT OF CAN BUS CHECK (CONNECTION STATUS CHECK USING TECHSTREAM) Inspect or repair the probable malfunctioning part based on the check result of step 6 (the step in which CAN Bus Check was performed). Result of CAN Bus Check (Connection Status Check Using Techstream) Result Proceed to All ECUs and sensors connected to the CAN communication system are displayed on the screen. (CAN bus circuit is currently normal.) A One of the ECUs and sensors connected to the V Bus is not displayed on the screen. (Open in ECU or sensor branch lines, or communication interrupted.) B In addition to the ECUs and sensors which are connected to the CAN communication system but are not displayed on the screen, there are ECUs or sensors for which the detection status changes (changes between detected and not detected) during the inspection. (Open in one side of ECU or sensor branch lines.) C NOTE: Non-installed ECUs or sensors will not be displayed. Do not mistake them for being in communication stop mode. It may be possible to select buses that do not have ECUs or sensors from the bus selection pull-down menu on the Techstream. This is not a malfunction. HINT: Regarding CAN Bus Check, refer to How to Interpret CAN Bus Diagnosis (CAN Bus Check) Screen. Refer to «DIAGNOSIS SYSTEM [07/2013 - 12/2013]»(ref-612381-S33318737382014042900000). If the detection status of ECUs changes during the inspection, one of the branch lines of a connected ECU or sensor may be open. (Signals from the ECU or sensor that has an open in one of its branch lines create electrical noise, affecting response to the Techstream and the ECUs and whether or not sensors displayed.) B --> GO TO COMMUNICATION STOP MODE TABLE. Refer to «PROBLEM SYMPTOMS TABLE [07/2013 - 12/2013]»(ref-612381-S33003132002014042900000) C --> GO TO OPEN IN ONE SIDE OF CAN BRANCH LINE. Refer to «Open in One Side of CAN Branch Line»(ref-612381-S26309206702014042900000) A: Go to next step CHECK RESULT OF COMMUNICATION MALFUNCTION CHECK (SELECT THE MALFUNCTIONING BUS) Inspect or repair the probable malfunctioning part based on the check result of step 5 (the step in which checking for communication malfunction DTCs was performed). HINT: When checking for communication DTCs, refer to How to Interpret Communication DTCs (DTCs that start with U). Refer to «DIAGNOSIS SYSTEM [07/2013 - 12/2013]»(ref-612381-S33318737382014042900000). If communication DTCs are stored, and all ECUs and sensors connected to the CAN communication system are displayed on the Communication Bus Check (CAN bus check) screen of the Techstream, a past malfunction that is currently not occurring is suspected. When a CAN branch of the V bus is malfunctioning, because the ECUs and sensors related to it detect the malfunction, the problem area can be determined using the combination of DTCs that are output. NEXT: Go to next step DTC COMBINATION TABLE Confirm the problem according to the combination of output DTCs regarding the CAN communication system. Refer to «DIAGNOSIS SYSTEM [07/2013 - 12/2013]»(ref-612381-S33318737382014042900000). Result Proceed to Combination of DTCs is not in DTC Combination Table A Combination of DTCs is in DTC Combination Table B HINT: CAN communication system history DTCs may indicate the problem if CAN communication system DTCs are output and all ECUs and sensors connected to the CAN communication system are displayed on "CAN Bus Check" of the Techstream. B --> GO TO COMMUNICATION STOP MODE TABLE. Refer to «PROBLEM SYMPTOMS TABLE [07/2013 - 12/2013]»(ref-612381-S33003132002014042900000) A: Go to next step IDENTIFICATION OF PROBLEM (PAST MALFUNCTION IN MAIN BUS OF V BUS) Connect the cable to the negative (-) battery terminal. Clear the DTCs using the Techstream. Perform the tests in Symptom Simulation to check the wire harnesses and connectors including those for V bus main bus lines. Refer to «HOW TO PROCEED WITH TROUBLESHOOTING [07/2013 - 12/2013]»(ref-612229-S16181698712014042900000). Based on the results of the check, inspect the parts that output DTCs to determine the malfunctioning part. HINT: If DTCs are output, do not turn the ignition switch off. NEXT: Go to next step REPAIR OR REPLACEMENT NEXT: Go to next step CONFIRMATION TEST* NEXT --> END

DESCRIPTION

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There may be an open circuit one of the V bus main lines and/or a DLC3 branch line when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is 64 ohms or higher.

This malfunction is not related to the lines of a CAN main bus branch or to ECUs or sensor connected a CAN main bus branch.

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There may be a short circuit between the V bus main lines and/or CAN branch lines when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is below 57 ohms.

*: for Automatic Transmission System

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There may be a short circuit between the V bus main lines and/or CAN branch lines when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is below 57 ohms.

*1: w/ Smart Key System

*2: for Automatic Transmission System

*3: for Automatic Air Conditioning System

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There may be a short circuit between one of the CAN bus lines and +B when no resistance exists between terminals 6 (CANH) and 16 (BAT) or 14 (CANL) and 16 (BAT) of the DLC3.

*: for Automatic Transmission System

There may be a short circuit between one of the CAN bus lines and +B when no resistance exists between terminals 6 (CANH) and 16 (BAT) or 14 (CANL) and 16 (BAT) of the DLC3.

*1: w/ Smart Key System

*2: for Automatic Transmission System

*3: for Automatic Air Conditioning System

There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminals 6 (CANH) and 4 (CG) or 14 (CANL) and 4 (CG) of the DLC3.

*: for Automatic Transmission System

There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminals 6 (CANH) and 4 (CG) or 14 (CANL) and 4 (CG) of the DLC3.

*1: w/ Smart Key System

*2: for Automatic Transmission System

*3: for Automatic Air Conditioning System

If an ECU or sensor is not displayed on the CAN Bus Check screen of the Techstream and some ECUs and sensors repeatedly appear and disappear from the screen when the CAN main bus lines are normal (there is no open, short, short to +B or short to GND in the main bus lines), there may be an open circuit in either of one pair of CAN branch lines.

HINT

If some ECUs and sensors repeatedly appear and disappear from the CAN Bus Check screen, communication between the normal ECUs (sensors) and the Techstream may be affected by the incomplete signals that are output from the ECU that has an open circuit in either of its CAN branch lines. In this case, the CAN branch lines for the ECUs and sensors that repeatedly appear and disappear from the screen are normal and the ECU that is not displayed on the screen may be the main cause of the problem (this ECU may have an open circuit in either of its CAN branch lines).

*: for Automatic Transmission System

If an ECU or sensor is not displayed on the CAN Bus Check screen of the Techstream and some ECUs and sensors repeatedly appear and disappear from the screen when the CAN main bus lines are normal (there is no open, short, short to +B or short to GND in the main bus lines), there may be an open circuit in either of one pair of CAN branch lines.

HINT

If some ECUs and sensors repeatedly appear and disappear from the CAN Bus Check screen, communication between the normal ECUs (sensors) and the Techstream may be affected by the incomplete signals that are output from the ECU that has an open circuit in either of its CAN branch lines. In this case, the CAN branch lines for the ECUs and sensors that repeatedly appear and disappear from the screen are normal and the ECU that is not displayed on the screen may be the main cause of the problem (this ECU may have an open circuit in either of its CAN branch lines).

*1: w/ Smart Key System

*2: for Automatic Transmission System

*3: for Automatic Air Conditioning System

See also:
• REMOVAL [07/2013 - ]
• ECM Power Source Circuit
• REMOVAL [07/2013 - ]