ELM327

Workshop glossary › Diagnostics & protocols · Updated 2026-04-16

An OBD-II interpreter chip designed by Elm Electronics in 2005. Wraps every OBD-II protocol behind a simple AT-command serial interface and powers most consumer Bluetooth/Wi-Fi OBD adapters.

The ELM327 is a microcontroller produced by Elm Electronics in Canada from 2005. It exposes an AT-command serial interface that hides the complexity of OBD-II protocol detection — the tool just sends an OBD-II request as ASCII, and the chip translates it into the right physical-layer protocol (ISO 15765-4, ISO 14230, ISO 9141-2, SAE J1850 PWM/VPW) automatically.

Almost every cheap consumer OBD-II adapter — the £10 Bluetooth dongle, the Vgate iCar, the OBDLink MX+ — is either a genuine ELM327 or a Chinese clone (PIC18F-based or, increasingly, custom ASIC). Genuine chips have version 2.2 firmware; clones often claim to be "v2.1" or "v2.3" and are missing CAN-FD support, accurate timing, and some service modes.

For workshop use the ELM327 is great for triage and customer-facing live data, but it is not a substitute for a manufacturer-level tool: it cannot do bidirectional UDS, security access, or ECU coding.