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OBD Inspection Using SAE J2534
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Overview Drew Tech System view of the OBD Interface
Options for OBD communications Benefits from standard interface DrewTech’s use of SAE J2534 in BAR Potential for other programs moving forward
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Drew Technologies Background
Products used for OEM Engineering, Diagnostics, End of Line testing, recall programs, and OBD testing Commercial relationship with global automakers Key supplier for essential tools and factory diagnostics programs in USA, Europe, and Japan Co-wrote several SAE standards including SAE J2534 and J1699 Support validation and testing of SAE and EPA standards for several OEMs
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Vehicle Interface Device Communications
Explain diagram of SAE J2534 PC Application OBD Interface Vehicle OBD API OBD API Vehicle Protocol ECUs
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OBD Interface Challenges
Each vendor’s OBD Interface communicates differently with a PC application With every IM program, a decision must be made: Option 1: Write your own API and comm. spec for the OBD Interface Option 2: Use a single vendor’s proprietary API and comm. spec This decision is very important, and will have implications throughout the entire program.
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OBD Interface Spec Choices
Choices IM programs face Option 1 Write a Customized OBD Comm Spec Option 2 Single Vendor Proprietary OBD Spec Advantages Allows the IM program to support multiple devices from different vendors Allows the IM program to design a system that gives them all of the data needed for future analysis IM program can easily switch between different OBD devices and vendors Disadvantages No communication spec is 100% perfect at first. A lot of effort is required for the IM program to figure out all of the details of how the com API works The IM program will need to create a validation test to make sure every device is compliant the level of effort is greatly reduced for the IM program because they can use what is already available The IM program will be forced to use one vendor, and cannot easily change vendors down the road There may be some limitations in the vendor’s device that reduces the amount of data that can be collected and analyzed. When there is a problem, who’s fault is it? The Device vendor or IM application? More difficult to determine without a written spec and compliance test
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Option 3: Develop with a Standard
In the service and repair world, almost all automakers globally are using a standard OBD Interface for their dealership diagnostic tools Advantages There are some standards that are already developed, tested, and proven Lower cost in program development Requiring a standard device allows more transparency among device vendors Easier to diagnose issues in the field if hardware is built to a standardized spec Will help OBD Interfaces become more of a commodity The most popular global standard for vehicle interfaces is SAE J2534
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SAE J2534 Standard SAE J2534 was created for emissions reprogramming
First version published in 2002, latest version will publish this year Initially intended for emissions programming, but was quickly adapted into other uses There are over 50 different software applications for diagnostics and reprogramming available today that can be supported from a J2534 interface. There are three versions: J2534-1, J2534-2, and J The base specification is J and it contains everything needed for emissions testing
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Legislation Requiring J2534
EPA - EPA requires OEMs to comply with SAE J2534 for pass-through reprogramming beginning with model year Reprogramming information be made available within 3 months of vehicle introduction for new models. For vehicles, EPA specifically allows OEMs to use J2534 technology on model year vehicles as long as OEMs make all additional hardware (i.e. cables) available for sale at a fair and reasonable price to the aftermarket to allow for the reprogramming of these vehicles. OEMs must make this additional hardware available for sale independently and cannot require the purchase of their OEM specific scan tool in order to receive this additional hardware. CARB - Beginning with the 2004 model year, reprogramming methods used for passenger cars, light-duty trucks, and medium-duty engines and vehicles shall be compatible with SAE J Paper, “Recommended Practice for Pass-Thru Vehicle Programming, September December 2004, which is Incorporated by reference herein, for all vehicle models that can be reprogrammed by franchised dealerships or authorized service networks. EURO V - Reprogramming of vehicle control units shall be conducted in accordance with SAE J2534. Massachusetts Right to Repair – Requires OEM Diagnostics and all module reprogramming using SAE J2534 for Model Year 2015 and newer vehicles.
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ETI J2534 Survey Results n=622 N=598
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Do you offer state-mandated OBD emissions testing for your customers?
ETI J2534 Survey Results Do you offer state-mandated OBD emissions testing for your customers? n=585
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Do you offer state-mandated OBD emissions testing for your customers?
ETI J2534 Survey Results Do you offer state-mandated OBD emissions testing for your customers? Since you perform OBD emission testing, would you like to be able to perform the test using your J2534 device? n=585 n=159
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SAE J2534 API Functions
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Drew Tech’s use of J2534 for BAR-DAD
Bar released the DAD hardware and Comm spec near the end of 2012 These specifications are proprietary and unique for California Developing a new piece of hardware for the DAD was expected to take up to 6 months, but DrewTech wanted to begin software development immediately Drew Tech wrote a “wrapper” to convert the BAR Comm. spec to work over SAE J2534 The J2534 wrapper allows DrewTech to prototype with any SAE J2534 device This rapidly accelerated development for DrewTech, allowing tests with usable hardware in instantly instead of waiting several months for the production hardware
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J2534 Testing Screenshot of the devices we could have used with our SAE J2534 wrapper
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Drew Tech’s use of J2534 for BAR-DAD
View of how DrewTech developed BAR DAD using SAE J2534 Proved concept that SAE J2534 is capable of emissions testing Final product will be changed to prevent tampering PC BAR OIS BAR Comm. Layer OBD Device Vehicle Drew J2534 Wrapper SAE J2534 Vehicle Protocol ECUs
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J2534 and Tampering SAE J2534 pushes the intelligence back into the PC application The messages being “passed thru” are direct communications to the vehicle It would not be beneficial for someone to insert a simulator between the J2534 devie and the PC because it would be more difficult than simulating the OBD2 end of the vehicle Using SAE J2534 also gives the IM program more direct control of the interface and access to more timing details Moving the intelligence to the PC allows the IM program to have more control over the “magic”. I.e. protocol determination order and handling special no-comm vehicles.
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J2534 Conclusions This exercise proved that SAE J2534 was capable of supporting emissions testing applications The same wrapper could be used to allow other IM programs to support OBD devices that use SAE J2534 Because J2534 supports multiple communications methods, it becomes easy for the IM program to support USB, Ethernet, Bluetooth, wireless, and cellular devices. Final version of DrewTech DAD software tool will have special security ensuring that only a certified DAD device will communicate.
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