Toyota training multiplexing networks

Technician Handbook 673 Electronic & Computer Controlled Systems Section Topics Multiplex Circuit • Additional Properties of MPX Protocols Diagnosis ECU DLC Technical Training ECU Hi LO ECU • BEAN Networks • LIN Networks • CAN Networks • AVC-LAN Networks • Gateway ECUs • Transmit/Receive Charts • BEAN Diagnosis • WORKSHEET: BEAN Network Diagnosis • DEMO: Diagnosing a BEAN Circuit • LIN Diagnosis • WORKSHEET: AC LIN Interface • CAN Diagnosis • WORKSHEETS: CAN Network Diagnosis (3) • AVC-LAN Diagnosis • WORKSHEET: AVC-LAN Inspection • Other MPX Circuits • WORKSHEET: A/C Bus Servo Motor Operation 83 673 Electronic & Computer Controlled Systems Technician Handbook Additional Properties of MPX Protocols Protocol: A set of rules and standards for communication between networked components Protocols establish the standards for a variety of possible network properties Properties: Conventions Communication Direction: One-way, two-way Transmission Timing: Periodic, event-driven Collision Detection & Recovery: Retransmission delay, priority scheme Data Casting: Broadcast, unicast, multicast Sleep Mode & Wake-up Function: Available, not available Additional Properties of MPX Protocols The network protocols in Toyota vehicles include: • BEAN • CAN • LIN • AVC-LAN Each protocol defines the rules and standards necessary for components on the network to communicate with one another Their rules and standards describe various network properties and their conventions This section discusses some of these properties and typical conventions in more detail 84 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Communication Direction One-way or two-way One-way communication (mainly used for Door Bus) Switch Signal (e.g P/W Open) Data Power Window Master Switch Main Body ECU Transmitter Receiver Two-way communication AC Compressor ON Data Data Engine ECU Transmitter Receiver Communication Direction • Water Temp • Ambient Temp A/C ECU Transmitter Receiver Communication direction is one of the considerations in multiplex network design Toyota networks may communicate in either a one-way direction or a two way direction The directional design provides for two different situations: In one-way communication, one component transmits data to another and waits for an acknowledgement In the example above, the Power Window ECU transmits data to the Main Body ECU that the power window switch is open The Main Body ECU only acknowledges receipt of the transmitted data Two-way data transmission involves data flowing in both directions – not just data and acknowledgement, but actual data in both directions In the example above, the Engine ECU transmits data related to the A/C compressor’s ON status and the A/C ECU acknowledges receipt of that data and replies with additional data related to the water and ambient temperature BEAN communication direction can be either one-way or two-way The CAN, LIN, and AVC-LAN are all two-way communication networks Technical Training 85 Technician Handbook 673 Electronic & Computer Controlled Systems Transmission Timing Periodic and event-driven Periodic Transmission Data which always needs to be updated is sent to participating ECUs periodically Water Temp Water Temp Sensor W W Engine ECU W W W Meter ECU Event Transmission Data is sent to participating ECUs when any of the relevant switches are operated ON OFF S Power Window Master Switch Switch Operation S Main Body ECU If a switch is operated during periodic data transmission, a switch operation signal is inserted between periodic data Periodic data transmission resumes after event transmission W S W S W W S W W Power Window Master Switch Engine ECU Main Body ECU Meter ECU Page 86 Transmission Timing Another network property taken into consideration in design is the transmission timing of the data Data may be periodically transmitted or it may be event-driven Periodic data, such as a water temperature signal or engine speed, is transmitted at regular intervals Event-driven data is transmitted when an event occurs, such as when a switch is thrown 86 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Collision Detection & Recovery Retransmission delay or priority scheme When two ECUs attempt to transmit data at the same time, a data collision occurs Data ECU Data ECU ECU ECU ECU Retransmission delay (BEAN) Each ECU stops transmitting for a predetermined time interval ECUs resume transmitting one after the other, with the highest priority ECU going first (10 kbps) Priority scheme (CAN) The ECU with the highest priority message is allowed to continue transmitting Other ECUs stop until the communication line is no longer busy (250 to 500 kbps) Collision Detection In a multi-master network (such as BEAN or CAN), collision detection is a method of resolving data collisions that might occur when more than one ECU transmits at the same time Multiple access to the serial data bus allows individual ECUs to function independently and transmit at any time they sense an idle network If a data collision occurs, the ECUs in some networks (such as the BEAN) each wait for a slightly different predetermined time interval and then resume data transmission The sequence in which they restart is based on their priority CAN uses a message priority method for resolving conflicts on the network When a data collision occurs, the ECU with the highest priority message continues transmitting while the other ECUs stop The other ECUs can resume transmitting when they detect the communication line is not busy By not interrupting transmission of the priority message, the CAN protocol is able to operate at faster speeds Both LIN and AVC-LAN networks are controlled by a master node, so no collisions can occur and arbitration or collision management in the slave nodes is not required Technical Training 87 Technician Handbook 673 Electronic & Computer Controlled Systems Data Casting Broadcast, unicast and multicast Broadcast Communication Data is sent from an ECU to participating ECUs ECU ECU ECU ECU ECU Transmit Receive Receive Receive Receive ECU ECU Unicast Communication Data is sent from an ECU to a certain ECU ECU ECU ECU Receive Transmit Multicast Communication Data is sent from an ECU to a group of other ECUs ECU ECU Transmit Data Casting ECU ECU Receive Receive ECU Another attribute of network protocol is data casting There are three basic types of data casting methods used • Broadcast communication where every node on the network receives the data • Unicast communication where data is only addressed to one node on the network and the address is ignored by the other nodes • Multicast communication where data is transmitted from one node on the network and addressed to a group of other nodes The Body Electronics Area Network can transmit data using all three types of data casting methods The Controller Area Network transmits using broadcast and multicast methods Individual ECUs can ignore sent data but will send a receipt of data transmission A CAN Bus Check is a broadcast signal which checks to confirm which ECUs are responding Replies are returned in the order of reception Local Interconnect Network transmits using the multicast method Audio Visual Communication-Local Area Network uses all three 88 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Sleep Mode & Wakeup Function Available or Unavailable Not all systems have sleep mode When a system with sleep mode judges that the vehicle is not being used, it stops communication of all ECUs to reduce parasitic current (BEAN, CAN, LIN) Sleep • IG-OFF • All doors are closed • After a predetermined time the system goes to sleep the affected ECU sends a “wake-up” message to other ECUs zz Wake-up signal ECU zz Wake-up During sleep, if any of the relevant switches are operated: • Open the door • Unlock the door, etc ECU zz ECU ECU ECU ECU What would keep the network from going to sleep? Sleep Mode In the BEAN and LIN protocols, ECUs periodically transmit data This activity uses battery voltage and creates a normal parasitic draw To reduce parasitic draw when the vehicle is not being used, ECUs enter “sleep” mode after a set time when the ignition is off and the doors are closed After the ignition has been turned OFF, a CAN node may also enter sleep mode to reduce the power consumption The transmitter portion of the transceiver module is switched OFF, however the receiver part can remain active to check for activity on the bus Wakeup Function When any network-related switch is operated, the associated ECU “wakes up” and sends a wake up signal to all the other ECUs on the network In a LIN network, both the master and slaves are able to wake-up the network AVC-LAN does not have a sleep mode and wake-up function SERVICE TIP • A dead battery from a parasitic draw can be caused by a BEAN, LIN, or CAN network that is not going to sleep • A network can be kept awake if one of the ECUs on the network is receiving constant input from a faulty switch or sensor • Circuits operating properly can also keep a network awake - an immobilizer key left in the key cylinder (with ignition off) for example Technical Training 89 Technician Handbook 673 Electronic & Computer Controlled Systems Body Electronics Area Network (BEAN) Topology: • • Daisy chain configuration to improve reliability in the event of open circuit Single-wire voltage drive (speed = 10 kbps) Theft Deterrent ECU MPX1 Bus MPX1 Power Seat ECU MPX1 Bus MPX2 MPX2 Driver Door ECU MPX1 MPX1 MPX3 Body ECU MPX2 MPX2 Passenger Door ECU MPX1 Ring MPX4 2004 Avalon Body Electronics Area Network The Body Electronics Area Network (BEAN) is a proprietary network developed by Toyota It is a low-speed protocol typically used for ordinary body electrical systems such as windows, doors, mirrors, seats, etc The BEAN uses a combination of the ring and bus styles to network its ECUs This style of connection is also called a daisy chain The advantage of a ring configuration is that the ECUs in the ring part of the network can continue to communicate even if there is an open in one area because the transmission can travel via two possible pathways Even in the ring configuration, if the communication line is cut at more than one point, communication becomes impossible In recent Toyota systems, however, a back-up bus is provided to maintain limited communications A backup bus usually links the combination switch, front Controller, and Main Body ECU Several BEAN networks may be connected to each other via a Gateway ECU or to other networks via the Gateway BEAN also provides the capability for customizing certain system settings using Techstream 90 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Local Interconnect Network (LIN) Master-Slave Protocol: • • • • Master sends request for data to the slave The slave responds with data requested Slaves cannot transmit unless requested (except for “wake-up” message) Slaves cannot communicate with each other Master ECU Slave ECU Slave ECU LIN Slave ECU Speed = 20 kbps Slave ECU (e.g Power Window Master Switch, Sliding Roof ECU, etc.) Local Interconnect Network LIN was developed by a consortium of European car manufacturers as a lower cost alternative to CAN Though its maximum transmission speed is only 20 kbps, its cost is two to three times lower per node It is typically used to control sensors and actuators in non-critical systems such as windows, doors, seats and air conditioning systems LIN Characteristics The LIN protocol uses an AV (automotive vinyl) single wire in a star topology to create a master-slave configuration Because each of the slaves are connected directly to the master, nodes may be added to the network without requiring hardware or software changes In the master-slave configuration, slaves can only communicate with the master, and can send data only after receiving a data request from the master Because each slave is separately connected to the master, a failure in any part of the network does not affect the rest of the network LIN Replacing BEAN Technical Training BEAN was developed by Toyota as a proprietary network before industrywide automotive networks were available Because LIN has now appeared as an industry standard and is also a low-speed, low cost network similar to BEAN, it is replacing BEAN in most newer Toyota vehicles 91 Technician Handbook 673 Electronic & Computer Controlled Systems Local Interconnect Network (LIN) Topology: • Master ECU is connected to the CAN network • Master serves as a gateway for up to 64 slaves • Single-wire voltage drive ECU ECU CAN (e.g Main Body ECU) ECU ECU Master ECU Slave ECU Slave ECU LIN Slave ECU LIN Gateway Function 92 Slave ECU LIN has a multiple slave network architecture with a message identification for multi-cast transmission between any network node It shares some of the features of an AVC-LAN network except that a LIN master ECU contains a gateway function which has the capability to interface with higher-level networks such as CAN This feature extends the benefits of networking all the way down to the individual sensors and actuators Technical Training 673 Electronic & Computer Controlled Systems Technician Handbook CAN BUS Check CAN Bus Check Location of DLC3 Using Techstream to perform a CAN bus check quickly identifies any ECUs that are not communicating Comparing these ECUs to the multiplex circuit diagram from the EWD can potentially help identify possible problem locations before performing vehicle diagnostics When analyzing the multiplex circuit diagram to locate the ECUs that are not communicating, also note the location of DLC3 A problem between the network and DLC3 can make it appear the entire network is down Also, when the vehicle has more than one CAN network, DLC3 is directly connected to only one of them By analyzing the ECUs that are communicating, you can determine which CAN network is experiencing trouble 120 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems CAN Terminating Resistors Know where the terminating resistors are located HS Bus MS Bus Disconnecting them will cause network communication to become unreliable Terminating Resistors The CAN high and CAN low communication lines are connected at each end by a terminating resistor This resistor helps to stabilize voltages on the lines and prevent “echoes.” The terminating resistors are almost always inside two of the ECUs on the network (In some vehicle models, a terminating resistor may be located inside a junction connector.) As the illustration above shows, disconnecting either of the ECUs containing an HS bus terminating resistor would create an open in the CAN bus and take the bus down All of the other components on the CAN HS bus are connected by sub bus lines Therefore these ECUs can be disconnected from CAN without creating an open in the main bus line Technical Training 121 Technician Handbook 673 Electronic & Computer Controlled Systems CAN Resistance Tests Check Bus Line (CANH – CANL) A OK! (54 to 69 Ohm) B NG (70 Ohm or more) C NG (Less than 54 Ohm) Check Bus Line (CG – CANH/L) CG – CANH CG – CANL NG B Open in CAN Bus Line C Short in CAN Branch Line OK! (200 Ohm or more) Short of CAN Bus line to CG OK! Check Communication Malfunction DTC (Past DTC) A Check Bus Line (CANH/L - BAT) CANH – BAT CANL – BAT NG OK! (6k Ohm or more) Short of CAN Bus line to BAT OK! Resistance Tests on CAN Circuits NOTE Does 60 ohms between CANH and CANL mean the network is OK? CAN diagnostic procedures in the Repair Manual call for various resistance tests that can be useful in identifying shorts and opens in the bus line To perform resistance testing on the CAN bus, the ignition must first be cycled OFF After turning the ignition off, it may take up to several minutes for capacitors to fully discharge and the resistance reading to stabilize Any readings obtained before the circuit has stabilized will not be accurate Resistance measurements will change slightly when Techstream is connected to the network via DLC3 122 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems CAN Resistance Tests ECU ECU ECU • CANH to CANL DLC Hi LO • CANH to BAT CG CANH • CANL to BAT • CG to CANH • CG to CANL 10 11 12 13 14 15 16 CANL Resistance Tests on CAN Circuits NOTE BAT When it comes time in the diagnostic process to measure the resistance between CANH and CANL, it doesn't take but a few extra moments to obtain all the other resistance measurements, too Doing so can provide a more complete picture of the bus status before arriving at a conclusion regarding the source of a problem Before making resistance measurements between the CAN bus and B+ or ground, disconnect the negative battery cable This prevents obtaining resistance readings through alternate paths When analyzing resistance measurements, more than one reading may be out of spec For example, there may be a 73 ohm reading between CANH and CANL and a 0.3 ohm measurement between CANL and CG If the only measurement taken was the out-of-spec resistance of CANH to CANL, the diagnostic flow chart on the previous page would indicate an open circuit In reality, an open circuit would create a very high ohm reading By making the other measurements, the 0.3 ohm reading between CANL and CG suggests a short to ground This would most likely be the problem rather than the slightly out-of-spec 73 ohm reading between the bus lines NOTE Technical Training When testing resistance at the DLC3 connector, keep in mind that in models with a more than one CAN bus, the DLC3 terminals may be testing only one of the buses To test other CAN buses, it may be necessary to use a different connector 123 Technician Handbook 673 Electronic & Computer Controlled Systems Worksheets (1 of 3) CAN Diagnosis Classroom Worksheet: In this worksheet you will build a strategy to diagnose a CAN network fault using the EWD, a Techstream CAN bus check, and the information provided Instructor Demo CAN Resistance Test Precautions In the shop, the instructor will demonstrate how improper methods can result in incorrect CAN resistance measurements >> 2006 RAV4 Multiplex Circuit Diagram (PDF) Use this space to write down any questions you may have for your instructor NOTES: 124 Technical Training 673 Electronic & Computer Controlled Systems Technician Handbook Worksheet (2 & of 3) CAN Main Bus Faults Shop Worksheet: In this worksheet you will: • Use an ohmmeter and a PicoScope to observe CAN High and CAN Low • Diagnose a short to ground and an open circuit on CAN High and CAN Low • Short CAN High to CAN Low to observe the results CAN Sub Bus Diagnosis Shop Worksheet: In this worksheet you will use the EWD and Techstream’s CAN Communication Bus Check to develop a strategy to diagnose CAN sub bus faults Use this space to write down any questions you may have for your instructor NOTES: Technical Training 125 Technician Handbook 673 Electronic & Computer Controlled Systems AVC-LAN Communication Signal Differential Voltage Drive • TX+ (similar to CANH) • TX- (similar to CANL) TX+ and TX- are both pulled high The rulers show the differential voltage is greater than 120mV 2v to 3v (+5V Scale, 5ms per division, x4 zoom) AVC-LAN Signal AVC-LAN uses differential voltage drive similar to CAN However, the high and low voltage signaling circuits – similar to CANH and CANL - are referred to as TX+ and TX- in AVC-LAN devices Also similar to CAN, the ends of the TX+ and TX- lines are joined by 120 ohm resistors Whereas the CAN bus line idles at 2.5V, the AVC-LAN idles at around 2V When communicating, AVC-LAN pulls the voltage high on both TX+ and TX- The line voltages have to differ by more than 120mV for the AVC-LAN system to recognize communication 126 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems AVC-LAN Diagnosis Starting Diagnostic Mode (with Multi Display) Vehicle Condition Procedure Method While pressing the “INFO” button, alternately turn the light control switch from OFF to TAIL times • SPD km/h • ACC or IG ON* *To quit the diagnostic mode, turn to IG OFF + TAIL OFF Method While in the display adjustment screen, alternately touch the upper and lower parts of the left side of the screen times Note: On some vehicles 2010 and beyond, AVC-LAN DTCs can be retrieved using Techstream AVC-LAN Diagnosis Technical Training Some vehicle models have AVC-LAN that functions independently of any of the other vehicle networks The AVC-LAN in other models, however, may communicate with other vehicle networks through a Gateway ECU or other ECU with a gateway function Before diagnosing the AVC-LAN, first be sure any other networks the AVC-LAN connects to are functioning properly 127 Technician Handbook 673 Electronic & Computer Controlled Systems AVC-LAN DTCs Code: 01-E0 Logical Address DTC Sub-Code: 110-00- Physical Occurrence Address Connection Count Confirmation # Logical Address Navigation ECU 01 = Communication control 58 = Navigation ECU 80 = GPS Receiver Multi Display 01 = Communication control 34 = Front passenger monitor Stereo Component Amplifier 01 = Communication control 61 = Cassette tape player sw 63 = On-dash CD changer DTC E0 = “Registration complete” signal from master device cannot be received Physical Address 178 Navigation ECU 110 Multi Display 190 Radio and Player 440 Stereo Component Amplifier Connection Confirmation # • The number of minutes after power-up when the DTC occurred Occurrence Count • The number of times the DTC has been detected Note: AVC-LAN codes are vehicle specific Always check the Repair Manual for the vehicle being serviced AVC-LAN DTCs AVC-LAN has a fairly robust self-diagnostic capability with diagnostic trouble codes consisting of five parts: Logical Address The logical address code ( a hexadecimal number) does not refer to a component; it refers to a function within a component The Navigation ECU, for example, has a Navigation ECU function (logical address = 58) and a GPS Receiver function (logical address = 80) Other components have their own unique functions with their own unique logical addresses An exception is the Communication Control function which every AVC-LAN component has This function’s logical address is 01 DTC The DTC is a hexadecimal number that defines the specific problem For each DTC, the Repair Manual has an explanation of the meaning and the corrective action or additional diagnostic steps Physical Address This hexadecimal number corresponds to specific AVCLAN components such as the Navigation ECU, audio head unit, stereo amplifier, multi-display, etc Connection Confirmation Number Upon power-up, the AVC-LAN master ECU checks all the slaves once per minute The connection confirmation number increases by one after every check When a DTC is detected, the connection confirmation number is included with the DTC information to indicate when the fault occurred in relation to power-up This can be useful in determining the sequence in which DTCs occurred Occurrence Count Provides a count of the number of times a DTC has been detected 128 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Worksheet AVC-LAN Inspection Shop Worksheet: In this worksheet you will create, monitor and diagnose a Stereo Component Amplifier malfunction involving an AVC-LAN circuit Use this space to write down any questions you may have for your instructor NOTES: Technical Training 129 Technician Handbook 673 Electronic & Computer Controlled Systems Other Multiplex Circuits BUS connectors in air conditioning servo motor circuits illustrate the advantages of a simple multiplex circuit BUS Connector Communication/Driver IC With Bus Connectors A/C Amplifier Communication IC CPU One 3-wire harness A/C M M M M Pulse-type Servo motors Without Bus Connectors A/C Amplifier Servo motors Drive IC CPU Drive IC A/C M Other Multiplex Circuits M M M Four 5-wire harnesses Although BEAN, LIN, CAN, and AVC-LAN are the most frequently used multiplex protocols in automobiles, other automotive systems may gain the advantages of multiplex communication by implementing their own special purpose protocols Dynamic laser cruise control is one example of a circuit that uses serial communication that is not BEAN, LIN, CAN or AVC-LAN The laser sensor and Distance Control ECU use their own special purpose multiplex protocol because of the complex communication required between them The significance of knowing this is that when you encounter a circuit described as “serial”, you’ll know to expect a fluctuating communication signal on that line instead of a fixed voltage A/C Servo Motor Circuits An air conditioning servo motor circuit is another good example of using multiplex circuits to reduce wiring The typical connection between the A/C amplifier and an ordinary servo motor requires five wires: • Two wires to the motor – necessary so forward or reverse current can be supplied to control motor direction • Three wires to the sensor circuit to determine motor position and direction To reduce the wiring between the servo motors and the A/C amplifier, pulsetype servo motors use a communications chip built into the servo motor connector This chip, called a BUS connector, communicates with the A/C amplifier using serial data (multiplex) communications In this configuration, only three wires are needed: • Power • Ground • Communication signal 130 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems BUS Connectors BUS Connectors with built-in communication/driver ICs allow the use of pulse-type servo motors and require less harness wiring BUS Connector Communication/Driver IC With Bus Connectors A/C Amplifier Communication IC IC CPU One 3-wire harness A/C M M M M Pulse-type Servo motors Bus Connector Note: If the color-coded connectors are not matched to the correct servo motors, the wrong motors will operate BUS Connectors The BUS connectors are sequentially arranged on a single harness to yield a bus network topology Each BUS connector controls its motor’s operation by translating serial data from the A/C amplifier on the communication signal line It then interprets pulses from the A, B, and GND contacts on the servo motor, converts them into serial data and transmits position information back to the A/C amplifier All the BUS connectors share the same communication line, so the serial data flowing to and from the connectors must include a connector ID This ID enables the connector to ignore A/C amplifier signals meant for another servo motor, and enables the A/C amplifier to determine which connector is transmitting its motor position information Because of this, if the connectors are not matched to the correct servo motors, the wrong motors will operate NOTE 131 Some newer vehicles have as many as 12 AC servo motors operating on three unique BUS connector networks In these vehicles, this special purpose multiplex protocol saves a considerable amount of wiring, contributing greatly to lighter weight, less expense, and greater reliability Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Pulse-Type Servo Motors Pulse-type servo motors transmit two ON/OFF signals to communicate damper position and movement direction Contact Points Printed Circuit Board A Servo Motor A B GND B GND Conduction A B High Low High Low Pulse-Type Servo Motors Also called pulse pattern type servo motors, these motors use a printed circuit board that rotates with the motor shaft to signal motor direction and position As the motor turns, the contact points at A and B open and close a circuit to create a coded pulse pattern that indicates the position of the damper doors Because the output signals from the motor are digital (ON/OFF), the communication chip that relays these signals does not need to perform analog-to-digital conversion This makes the communication chip much simpler, smaller, and less expensive 132 Technical Training Technician Handbook 673 Electronic & Computer Controlled Systems Worksheet A/C Bus Servo Motor Operation & Diagnosis Shop Worksheet: In this worksheet you will monitor Bus Connector and Servo Motor operation using Techstream DATA LIST and a PicoScope to deduce communication problems with the A/C System Use this space to write down any questions you may have for your instructor NOTES: Technical Training 133 673 Electronic & Computer Controlled Systems Technician Handbook This Page Intentionally Left Blank 134 Technical Training ... between the BEAN, CAN, and AVC-LAN networks Gateways also regulate the exchange of data between networks of the same protocol, such as two BEAN networks Separate BEAN networks ensure that a failure... rest of the network LIN Replacing BEAN Technical Training BEAN was developed by Toyota as a proprietary network before industrywide automotive networks were available Because LIN has now appeared... Both LIN and AVC-LAN networks are controlled by a master node, so no collisions can occur and arbitration or collision management in the slave nodes is not required Technical Training 87 Technician