Diagnostics using OBD II data bus communication networks
Contents
1. DSG Airbag CM J234 Steering Angle Sensor G85 Steering Wheel CM E221 Ignition Starter Switch D Steering Column Electronic Systems Wiper Motor CM J400 Rain Light Recognition Sensor G397 Drivetrain CAN bus Alarm Horn H8 Convenience CAN bus Infotainment AN bus LIN Bus Instrument Cluster CAN bus CAN bus Wire Communications Line e low med speed data of 1k bit s to 20k bit s Single wire CAN D Multimedia Cost effective Uses various protocols No real time requirements e Real time data 1M 400M bit sec e Fiber optic network protocol with capacity for high volume streaming include automotive multimedia and personal computer networking The graphic on the next page shows a fiber optic CAN D network Page 11 OBD II Network Diagnostics NOTES Page 12 BOSCH A Growing List of CAN Applications Below is a list of some vehicles that are currently in CAN compliance CAN compliant means that the CAN network broadcasts diagnostic information to the scan tool Pins 6 amp 14 or3 amp 11 in CAN protocol language Many scan tools have to be updated with CAN module adapters to communicate at the higher baud rates that CAN systems produce 2003 Ford Excursion 2003 Ford F 250 and F 350 2003 Ford Focus and Thunderbird 2003 General Motors Saturn ION 2003 Lincoln LS 2003 Mazda 6 2003 Saab 9 3 2004 Buick Rendezvous 2004 Cadillac CTS XLR and SRX 2004 Dodge Durango 2004 Ford Ex2. High voltage is Vbatt Just because a vehicle has an ISO protocol does not mean that the control modules are unable to talk to each other An example would be a 2001 Volkswagen Passat where the modules talk to each other on a CAN protocol network The CAN protocol is then transmitted to the IP instrument cluster module where the signal protocol is converted to ISO format for communication with the scan tool Freeze Control TTTTTTTTT Example Waveform Recall Run Save M BEEN EPIRI Time Div i i CH 1 5 00V DC CH 3 OFF CH 2 5 00 Y DC CH 4 OFF Level 5 00 V Nrml E Source CH 1 Falling Edge MTS 5200 Engine Analyzer Vetronix Bosch Group 01 Mar 2007 12 55 45 ISO 9141 2 ISO 14230 In use by 1997 ISO 14230 was an upgrade to ISO 9141 2 One of the major enhancements of ISO 14230 was a faster wake up call ISO 14230 KWP2000 Keyword Protocol 2000 Pin 7 K line Pin 15 L line optional Physical layer identical to ISO 9141 2 Data rate 1 2 to 10 4 kbaud 39 BOSCH OBD II Network Diagnostics CAN Systems NOTES Controller Area Network or CAN is the latest communication system within the automotive world CAN is a means of linking all of the electronic systems within a car together to allow them to communicate with each other As on board computers increase so does the number of different electronic systems Today s modern vehicles may have as many as 50 or more on board computer system
3. Invented for life
4. B O S C H OBD II Network Diagnostics Diagnostics Using OBD Il NOTES Data Bus Communication Networks Overview Vehicle On Board Control Modules are changing the automotive industry in two related areas The first area concerns the expansion and use of multiple on board control units Today s modern vehicle will have on board control modules controlling vehicle components such as the engine antilock braking system transmission instrument panel chassis and body control functions to name just a few An on board control module does more than just make Sure its own input and output devices work correctly The on board controller also participates and communicates in one or more communication networks in the vehicle These vehicle networks exist to allow the sharing of information among components and to reduce the numbers of wires and sensors required in the vehicle The second area in which microcontrollers are changing the automotive industry concerns the way we interact with our vehicles Computers are now common in the passenger area and consumers can now interact with their vehicles in a variety of ways This allows consumers to run already familiar programs in the vehicle email GPS navigation calendar management etc Lexus Navigation Center Page 1 OBD II Network Diagnostics NOTES Page 2 The second phase of this migration also allows the automotive technician to interact with the vehicle s on board co
5. modern vehicles adding more advanced on board diagnostics Control modules are now programmed to know what other modules they should be in communication with on the network Based on network communication problems a U code could be set if a particular module was not communicating on the network Flash reprogramming new control modules is necessary because new control modules need to know how that particular vehicle is configured in order to perform their function on the network properly e The first character identifies the system related to the trouble code P Powertrain B Body C Chassis U Network for years U was undefined Page 17 OBD II Network Diagnostics NOTES Page 18 9 BOSCH Example of Generic U Codes U0100 Lost Communication With ECM PCM A U0101 Lost Communication With TCM U0102 Lost Communication With Transfer Case Control Module U0103 Lost Communication With Gear Shift Module U0104 Lost Communication With Cruise Control Module U0105 Lost Communication With Fuel Injector Control Module U0106 Lost Communication With Glow Plug Control Module U0107 Lost Communication With Throttle Actuator Control Module U0108 Lost Communication With Alternative Fuel Control Module U0109 Lost Communication With Fuel Pump Control Module U0110 Lost Communication With Drive Motor Control Module U0111 Lost Communication With Battery Energy Control Module A U0112 Lost Communication Wi
6. necessary before troubleshooting can begin e Preliminary checks Operate the suspect system and evaluate its performance Perform a thorough visual inspection of all components including fuses connectors grounds and harness routing This is also an ideal time to pull up the service history on the vehicle e Perform published diagnostic system checks If there is a published diagnostic procedure that will help you narrow down the cause of the problem use it first Note This is the time to connect the scan tool and request diagnostic information from the control modules on the network e Check for bulletins If you have access to published service bulletins for the vehicle search those for a possible fix This can save time in the long run You can also print safety bulletins for your customers at this point as an added value e Stored diagnostic trouble codes DTC s and symptoms with no DTC s If there is a hard trouble code then follow the diagnostic procedure for the particular DTC If you have a repeatable symptom then use the oymptom Charts Both these procedures will quickly help you narrow your diagnostic focus e No published diagnostics When there is no DTC stored and no matching symptom for the condition in the service manual you will have to develop your own diagnostic process based on your understanding of how the circuit operates This is the time when there is no substitute for advanced systems training The grap
7. 3 OFF CH 2 2 00 V DC CH 4 OFF f Level 2 00 V Nrml Source CH 1 Rising Edge MTS 5200 Engine Analyzer Vetronix Bosch Group 09 Jan 2007 13 21 57 SAE J1850 PWM MTS 5100 Robert Bosch LLC Page 6 BOSCH General Motors Class 2 Bus Protocol operates at 10 4 kB sec with one communication wire Chrysler also has an adaptation of the GM Class 2 protocol Pin 2 Bus Bus idles low High voltage is 7 V _ Decision point is 3 5 V Message length is restricted to 11 bytes including CRC Component Selection Trig Setup Lead Glitch Help On Defalt Signal Setup Finder 4 p Time Div mg Level 3 25 V Nrml T Source CH 1 Rising Edge DR dan MNA 12 24 25 lt SAE J1850 VPM ISO 9141 2 from the European influenced International Standards Organization This is a single wire where the ISO modules talk only when asked and only to the scan tool not to each other This protocol is slower than GM and Chrysler versions of SAE J1850 The ISO 9141 2 protocol has a long wake up call which allows for each control module to report PID data ISO 9141 2 protocol has a data rate of 10 4 kbaud and is primarily used in Chrysler European and Asian vehicles OBD II Network Diagnostics NOTES Page 7 OBD II Network Diagnostics NOTES Page 8 Pin 7 K line Pin 15 L line optional UART signaling though not RS 232 voltage levels K line idles high
8. C Hi NOTES Trigger source Mode Ch2 cut Auto Time Diagnosis RN au WSUe nnn Cn Sa ns SPSSHERBZ re Screen Capture using KTS 570 lab scope Robert BoschLLC Internal CAN Communication CAN networks can communicate internally but not with the scan tool Many CAN modules will talk with each other and a gateway or translator module will convert the protocol so a scan tool can understand it CAN Translators VW Example Instrument clusters from 08 99 gt are integrated into the vehicle CAN Data Bus network The CAN Bus on board diagnostic Interface J533 which is integrated into the instrument cluster enables data to be exchanged between the vehicles CAN Data Bus network and the Data Link Connector DLC K wire The CAN Bus On Board Diagnostic Interface J533 has specific on board diagnostic OBD capabilities that are accessed by using scan tool address word 19 Gateway The next page shows a network diagram of a VW Passat with three different networks Page 10 BOSCH Connector DLC T16 Scan Tool CAN Data Bus On Board Diagnostic Interface J533 Infotainment CAN Volkswagen Passat showing four different networks CAN A Comfort amp Convenience Systems Scan Tool ISO or KW Line Engine Control Module J220 RO Instrument Cluster CM J285 Anti Theft Engine Disable Immobilizer IV CM J334 Convenience CAN OBD II Network Diagnostics NOTES
9. e is generally used allowing high stability with enhanced fault localization This system is used in drivetrain and body network systems Ring Short path interconnection of multiple ECU s in a fiber optic series ring The information passes through each ECU This system is used in multimedia networks Multimedia systems require a large volumes of data to be transferred in short amounts of time To transmit a digital TV signal with 3 stereo sound requires a data transfer rate of around e 6 Mbit s MOST Media Oriented Systems a A Transport can transfer data at a rate of 21 2 Mbit s ri 5 Star Interconnection of multiple ECU s in a star FT FT structure network control by central master ECU FT This system uses a master slave time triggered protocol The network is designed as a low cost local sub system single wire interconnect network for use in on off devices such as car seats door locks sunroofs rain sensors and door mirrors Terminating Resistors Terminating resistors are used in CAN systems to create proper electrical load between the CAN H and CAN L circuits This load helps to reduce electrical noise on the data circuits which allows for a cleaner voltage signal on the data bus Terminating resistors in the high speed CAN systems are required to be 120 ohms with a maximum range of 118 132 ohms Lower speed CAN systems may use different values CAN systems can use split termination which means there may be mor
10. e than two terminating resistors in the system Terminating resistors may be physically located inside any of the control modules connected to the CAN harness with a junction connector The resistors may also be part of the wiring harness Terminating resistors may or may not be identified in circuit wiring diagrams Do not attempt to conduct wiring diagnostic fault procedures such as voltage or resistance tests without proper service information The figure on the next page shows an example of a CAN system with terminating resistors 3 BOSCH OBD II Network Diagnostics NOTES Traction Control 3 HEROS MEN mE 120 0 i 10 Lateral Acceleration Sensor Signal protocols There are five basic signal protocols currently in use with the OBD II interface SAE J1850 PWM SAE J1850 VPM ISO 9141 2 ISO 14230 KW ISO 15765 CAN C amp B Li ey ISO 15765 4 CAN Hi Bus ll ISO 15765 4 CAN Low Bus Page 5 OBD II Network Diagnostics BOSCH NOTES J1850 from the Society of Automotive Engineers Protocols Ford Standard Corporate Protocol Protocol operates at 41 6 kB sec with two wires on the bus SAE 41850 PWM 41 6 kbaud standard of the Ford Motor Company Pin 2 Bus Pin 10 Bus High voltage is 5 V nr tthe ora SOS Saw 01 09 2007 01 11 37 PM Example Waveform nA Recall Run T i MA TET meng Save BE Cursor Time Div 200 Secs CH 1 2 00 V DC CH
11. hic on the next page shows the diagnostic flow chart for Strategy Based Diagnostics Page 13 OBD II Network Diagnostics NOTES Page 14 BOSCH 11 Verify the customer concern 23 Perform preliminary checks Perform operational system check s O Check bulletins and other service information No DTC D No Matching Intermittent Select the symptom Rafer tn dirtemiiient Symptom from symptom chart sdk cokes rec Develop diagnostics and follow pe from wiring chart recommendations theory DTC Stored Follow the designated DTC table to repair Vehicle operates as designed Explain operation to customer Find isolate the Re examine the problem Concern g Repair Resolve Verify fix Verify the Customer Concern Expanded Know how the vehicle systems operate the driving habits of the customer and the environmental driving conditions The figure on the next page shows a 2001 VW Passat Central Locking Module located in a pan below the driver s seat Mud and snow can leak into this box and short out the computer thus killing the communication with the Scan Tool At this time there is no TSB on this problem but you can find information on the problem by browsing the Internet Even though the Internet is a great resource for information you should take the time to make sure the information is accurate by checking other websites Note Bosch does not support promote or endorse any
12. hicle driveability problems with networked computer modules know what computers are on the network for the particular vehicle application you are working on Many vehicle applications may add or delete computer modules based on the amount of accessories and options Most electronic information systems will have a computer network schematic at the beginning of the wiring diagrams section 14 1 Module Communications Network System overview Hot at ail Central Junc Electronic park Rear Electronic ABS control Powertrain Con times tion Box CJB brake module Modules REM module 20213 trol Module a S 144068 138520 PCM 124650 Front Electronic Driver east Module FEM module 1385525 14C718 ABS test con nactor Restraints con Auxillary Junc trol module tion Box AJB 148321 interior Audio unit instrument cius Electronic Auto ABS control 18508 ter matic Tampera module 20213 ture Control EATC module 19580 Powertrain Con Joint connector trol Module 4 PCM 124650 Data Link Con nactor DLC 14489 H H Courtesy Ford Motor Company Ford Motor Company Network Schematic Ford Technical Publications http www fordinstallersupport com The Invention of the U Code U codes were classified by the SAE as the 4 item for trouble code descriptions In the early years of OBD II the U designation was classified as undefined U codes are becoming more prevalent on today s
13. ms by eliminating miles of wires connections and splices With networking a fuel pump circuit that would normally be wired to the PCM to be commanded on could now be wired to a Rear Control Module REM reducing wire length and potential circuit problems With networking the command from the PCM to turn on the fuel pump could be sent to the REM module over the network that would then activate the fuel pump circuit Note As networks evolve look for control modules to be located in various quadrants within the vehicle and components located near that quadrant reporting to a specific control module Electrical terminal diagram 2 Engine control unit ABS control unit Automatic transmission control unit Airbag control unit A C control unit Central electronics control unit 1 Central electronics control unit 2 Central electronics control unit 3 Instrument cluster Steering column module Diagnosis socket OBD GS102505 11 TE A6 29 A6 22 Fir tirar d Ed 10 9 19 A 3 2 9 8 A LA on 2d x a ha is 14 16 31 E 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 2004 Volvo S 80 Control Module Network Confiauration Circuit Diagram from CAS SIS Diagnostics ESlI tronic Robert Bosch LLC Page 3 OBD II Network Diagnostics NOTES Page 4 3 BOSCH Network Topology Linear Interconnection of multiple ECU s on common linear bus A multi master principl
14. ne of these grounds may be open or have high resistance There is also a possibility that the scan tool might complete a ground that is faulty when the scan tool is not connected If the OBD connector has power or ground problems you should validate the connections when the scan tool is removed OBD II Network Diagnostics NOTES Page 15 OBD II Network Diagnostics NO TES ontro sis 1 channel multimeter measurement Exit multimeter with 50 0 000 um 50 12 11V afa po a a aa fs gt start A E L E a Bosch appicationsm fimBosce Controlun Yjunttied onp rat Q5 OREL OD RORIS incom Checking Power to Chassis Ground KTS 570 Robert Bosch LLC Using the scan tool in conjunction with a 16 Pin Breakout Box Different types of 16 Pin breakout boxes are available in the aftermarket Some breakout boxes hook up in parallel allowing you only the ability to probe the circuit with a scope or DVOM Other breakout boxes like the AES Line Spi hook in a series circuit allowing the scan tool to command data bus protocols from the on board computer while diagnosing with a lab scope or DVOM mastertech E A fi DE PF it ve je Je BU DE J ARRE AES LineSpi MTS 5200 MTS 3100 connected to Ford ISO 9141 2 in Module Status Check www aeswave com Page 16 B BOS C E OBD II Network Diagnostics What Computers Are Talking on the Network NOTES When diagnosing ve
15. ntrollers gathering information controlling the vehicle directly and aiding in the diagnosis of problems This interaction can occur with the use of a scan tool or in some case accessing the on board controller directly through an operation sequence or a control panel on the vehicle 2005 Dodge Neon with Idle Air Control Motor DTC P0508 This code was obtained by H E cycling the ignition key on off three times Notice how the code is displayed directly on the dash panel KTS 200 Communicating with Generic OBD ll interface Robert Bosch LLC Network and Scan Tool Communication An automotive controlled network consists of multiple series of control modules electronically communicating complex information and requests in a digital language format This digital language is known to technicians as vehicle protocols Modules can be connected on the network in serial or parallel interface The term used for this type of communication interface is called Multiplexing and can be carried through single or dual circuits When a scan tool is connected and interfaced into the network it should be considered as one other control module on the network B BOSCH OBD II Network Diagnostics Primary Purposes of Networking NOTES One of the major driveability concerns in automotive diagnostics is circuit related problems due to bad connections creating opens shorts resistance and voltage drop problems Networks help resolve these proble
16. plorer 2004 Ford F 150 E 250 and E 350 2004 Ford Taurus 2004 Lexus LS430 2004 Mercury Mountaineer 2004 Mercury Sable 2004 Mazda 3 and RX 8 2004 Toyota Prius 2004 Volvo S40 2005 Audi A4 and A6 2005 Chevrolet Equinox 2005 Chevrolet Trailblazer EXT 2005 Dodge Dakota and Magnum 2005 Ford Escape and Expedition 2005 GMC Envoy ESV and XL 2005 Jeep Grand Cherokee 2005 Lincoln Town Car 2005 Pontiac G6 Grand Prix and GTO 2005 Mazda MPV and Tribute 2005 Saab 9 7X 2005 Cadillac STS 2005 Chevrolet SSR 2005 Chrysler 300C 2005 Ford E 150 2005 Ford Freestyle 2005 Isuzu Ascender 2005 Lexus LS400 and GX470 2005 Mercury Mariner 2005 Land Rover LR3 2005 Mercedes Benz SLK350 2005 Toyota Avalon 2005 Buick LaCrosse Rendezvous and Rainier 2005 Chevrolet Cobalt Corvette and Malibu 2005 Mercury Grand Marquis Montigo and Sable 2005 Ford Crown Victoria Five Hundred Focus and Mustang 2005 Toyota 4Runner Sequoia Tacoma and Tundra 2005 Volvo S60 S80 V50 V70 XC90 39 BOSCH OBD II Network Diagnostics Strategy Based Diagnostics NOTES General Motors developed strategy based diagnostics for their technicians and the diagnostic procedure can be used on all vehicle applications e Verify the customer concern A technician needs to know how the system is supposed to function normally before deciding that the system is malfunctioning A thorough customer interview or a diagnostic worksheet filled out by the customer is
17. s on them The information recorded and processed by each control module is often used by one or more control modules on the system A requirement for a standardized means of quickly passing information between the control modules was needed leading to the development of CAN CAN History CAN protocol was created in 1984 by Robert Bosch Corporation with anticipation of future advances in on board electronics The first production application was in 1992 on several Mercedes Benz models CAN is now being used on more and more new vehicles By 2008 all new vehicles sold in the U S will be required to have a CAN compliant diagnostic system CAN Protocols ISO 15765 CAN B amp C CAN B the medium speed network nominally about 125 kB sec will be used for body electrical systems and normally will operate at 83 3 kB sec On some Mercedes cars there may be as many as 30 modules on the CAN B bus Pin 3 CAN High Pin 11 CAN Low CAN C is a 500 kbit s high speed two wire system for powertrain transmission and ABS modules CAN C is intended to operate at a 500 kB sec baud rate about 50 times faster than GM s Class 2 data bus version of J1850 and over 60 times faster than ISO 9141 2 Pin 6 CAN High Pin 14 CAN Low Note that Pins 4 chassis ground 5 signal ground and 16 battery positive are present in all configurations The next page shows a CAN High and CAN Low waveform Page 9 OBD II Network Diagnostics B BO S
18. th Battery Energy Control Module B U0113 Lost Communication With Emissions Critical Control Information U0114 Lost Communication With Four Wheel Drive Clutch Control Module U0115 Lost Communication With ECM PCM B U0116 Reserved by Document UO117 Reserved by Document U0118 Reserved by Document U0119 Reserved by Document U0120 Reserved by Document U0121 Lost Communication With Anti Lock Brake System ABS Control Module Example of GM Manufactured Specific U Codes U1000 Class 2 Communication Malfunction U1001 U1254 Loss of XXX Communications U1002 U1015 Loss of serial communications for Class 2 devices U1016 Loss of Class 2 Communication with VCM U1016 Loss of Communications with PCM U1017 U1025 Loss of serial communications for Class 2 devices U1026 Loss of ATC Class 2 Communication U1027 U1039 Loss of Serial Communications for Class 2 Devices U1040 Loss of Class 2 Communications with ABS U1041 Loss of EBCM Communication U1042 Lost Communications with Brake Traction Control System U1043 U1055 Loss of Serial Communications for Class 2 Devices U1056 Loss of Communications with RSS U1057 U1060 Loss of Serial Communications for Class 2 Devices U1161 Loss of PDM Serial Data Bosch Diagnostics conducts courses on this subject as well as many other topics in the field of automotive and diesel technology For more information on courses in your area go to www boschtechinfo com or call 800 321 4889 BOSCH
19. websites other than its own company website www Bosch com BOSCH 4393 Central control module for comfort system e in protective box floorpan cavity under driver s seat carpet Graphic captured from the Internet Perform published diagnostic system checks expanded Connecting the Scan Tool Is there power on Pin 16 to power up the Scan Tool Many OEM scan tools may not have internal batteries and will require Pin 16 to have power in order for the scan tool to communicate Be aware that no power on Pin 16 may affect some aftermarket scan tools consult your operator s guide Many times Pin 16 will not have power due to something as simple as a blown cigarette lighter fuse Remember Pin 16 is Battery Power Un switched Many technicians panic when their scan tool doesn t power up off the 16 Pin connector In some cases the technician will think the computer or computer s are dead and not communicating with the scan tool A quick work around is to power up the scan tool through an alternate battery source or AC power source Remember Pin 16 has nothing to do with communication it is only there to power up your scan tool for diagnosis Pins 4 amp 5 are also important as one of these grounds will be needed for your Scan Tool to power up the OBD II link and establish a reference link for scan tool communication If you are having communication problems it is imperative that you check the integrity of these grounds In some instances o
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