The ELM327 is a universal pre-programmed chip used for exchanging data between a device (laptops, smartphone handheld OBD reader) and the OBD interface (on-board diagnostics in the car). The ELM327 chip is widely used in OBD II reading equipment from many manufacturers.
The chip is used to exchange OBD vehicle data via a command protocol using a USB, Low and High speed RS-232, Bluetooth, wired or WIFI connection with a mobile phone, laptop, or another reading device.
There are also many clones of the ELM327 in circulation, mostly with version number v1.5. Furthermore, the clones often do not have OBD II port pins 2 and 10 connected. As a result, reading manufacturer-specific data is not possible. The versions issued by the manufacturer ELM Electronics are, however, versions V1.0, V1.3a, V1.4b, V2.1, and V2.2.
The old reading interfaces have the ELM323 chip. This is used for old vehicles with, for example, only a K-line as a communication line with various ECUs. The K-line is connected to pin 7 of the OBD connector / OBD port.
The ELM327 has, among other things, the capabilities to perform the following functions:
- Read and display fault codes.
- Read and display (limited) brand-specific fault codes.
- Clear fault codes.
- Reset MIL (Check Engine) dashboard light.
Display of real-time sensor values, including:
- Engine RPM
- Boost pressure
- Coolant temperature
- Fuel pressure
- Vehicle speed
- Fuel pressure
- Vehicle speed
- Fuel pressure
- Vehicle speed
- Fuel short term adaptive value
- Fuel long term adaptive value
- Intake manifold pressure and temperature
- Ignition advance
- Air mass
- Throttle position
- Lambda sensor voltages
- Fuel System Status
The supported ELM327 protocols are:
- SAE J1850 PWM (41.6 kbit/s)
- SAE J1850 VPW (10.4 kbit/s)
- ISO 9141-2 (5 baud init, 10.4 kbit/s)
- ISO 14230-4 KWP (5 baud init, 10.4 kbit/s)
- ISO 14230-4 KWP (fast init, 10.4 kbit/s)
- ISO 15765-4 CAN (11 bit ID, 500 kbit/s)
- ISO 15765-4 CAN (29 bit ID, 500 kbit/s)
- ISO 15765-4 CAN (11 bit ID, 250 kbit/s)
- ISO 15765-4 CAN (29 bit ID, 250 kbit/s)
- SAE J1939 (250kbit/s)
- SAE J1939 (500kbit/s)
It is important for proper functioning that the power supply and ground (GND) of the ELM327 are connected to the power supply and ground (GND) of the OBD connector/DLC connector (Data Link Connector) in the vehicle, to prevent interference caused by potential difference (voltage difference) between the chip and the vehicle. To ensure that the reading connector first makes contact with the ground, the ground pins of the connector are longer than the other pins.
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