ELM327 copies were widely sold in devices claiming to contain an ELM327 device, and problems have been reported with the copies. Pirates could trivially produce an ELM327 clone by purchasing the same microcontroller chip and programming it with the copied blob. Consequently, anyone who had bought a genuine ELM327-v1.0 could use a device programmer to read ELM's proprietary microcontroller firmware as a binary blob. When ELM Electronics sold version 1.0 of its ELM327, it did not enable the copy protection feature of the PIC microcontroller. The ELM327 is a PIC microcontroller that has been customized with ELM Electronics' proprietary code that implements the testing protocols. Typical cheap ELM327 copy without label on the controller

The ELM327 command set is similar to the Hayes AT commands. Oxygen sensor voltages/associated short term fuel trims.Clear some trouble codes and turn off the MIL ('Malfunction Indicator Light', more commonly known as the 'Check Engine Light').Read diagnostic trouble codes, both generic and manufacturer-specific.The function of such software may include supplementary vehicle instrumentation, reporting and clearing of error codes.

There are a large number of programs available that connect to the ELM327. The ELM327 abstracts the low-level protocol and presents a simple interface that can be called via a UART, typically by a hand-held diagnostic tool or a computer program connected by USB, RS-232, Bluetooth or Wi-Fi. Main article: On-Board Diagnostics § Applications

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