Road vehicle diagnostics using bluetooth

Most modern road vehicles today utilise the CAN bus for internal communication between sensors, instruments and control units. It is a bus that is cheap, reliable, durable against electrical disturbances and well suited for the vehicle industry. While the acceptance of the CAN bus has grown over the years, so has the need to standardise services possible to perform using this network. A document called ISO 14229-1 has been put together that will cover these issues, and can hopefully be accepted as a world standard of services in a near future.

ISO 14229-1 covers everything from testing the exhaust levels of the fumes, to reading sensor values or downloading new software. The set of services that can be performed is referred to as Diagnostics. If an error occurs, for instance a sensor reports erroneous values, this is logged as a Diagnostic Trouble Code in the control unit. It is now possible when fixing the vehicle to extract and interpret the trouble code, which yields the problem, and by this replace the faulty sensor.

When accessing the CAN bus a cable has to be connected to the vehicle. The cable limits freedom of movement, which can cause a lot of annoyance. An example would be when a mechanic performs tests with his scan tool. Say that he wants to check that all the lights on a truck are operable. He or she needs a really long cable to reach around the trailer. A wireless link would be a far better alternative. The Bluetooth technology could be used as link between the tool and the vehicles CAN bus. This thesis investigates and implements a solution on how to perform diagnostic services using Bluetooth as a gateway between the diagnostic terminal and the CAN bus of a road vehicle. The implementation covers a set of services according to ISO 14229- 1, including the download function.

Author: Enstrom, Par; Svedback, Erik

Source: LuleƄ University of Technology

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