Diagnost is free ELM327 software for PC: Windows 7 through 11, English and Russian interface, no ads, no license keys, no trial timer. It is built for the person who owns the car rather than for a workshop - plug the adapter in, press one button, and the program identifies the adapter, identifies the car from its VIN and lists the modules that reported faults, each explained in plain language.
The reason to run it on a laptop instead of a phone app is depth. OBD-II as a legal standard covers the engine and emissions systems and nothing else. ABS, ESP, transmission, airbags, body and climate modules answer manufacturer requests over UDS and KWP at their own addresses. Diagnost knows those addresses and sweeps them, so a cheap adapter behaves like a multi-system scanner on any CAN-bus car, roughly 2008 and newer.
What you get with a plain ELM327
- Faults from every module that answers, with an explanation of what to check and in what order;
- live sensor data, interactive graphs and trip recording for intermittent faults;
- freeze frame from the moment the code set, plus emissions readiness monitors;
- a vehicle ID card: VIN, CALID and CVN, ECU names and software versions;
- Toyota and Lexus hybrid battery reports - every block voltage, the spread between them and a verdict (Prius 2, 3 and 4, Aqua, Auris HSD, CT200h, Camry Hybrid, RX400h and RX450h);
- clearing codes for the whole car or one module, with a module backup taken first;
- session history per VIN, so you can see what changed since the last visit;
- a built-in AI mechanic that queries the modules itself and explains the result.
Coverage by make
| Make | What an ELM327 reaches |
|---|---|
| Toyota, Lexus, Daihatsu (2006+) | Module scan with Toyota addresses, hybrid battery report |
| VW, Audi, Skoda, SEAT (2008+) | Module scan with VAG addresses. The 2004-2008 TP2.0 module was added in 3.1.13 and is being verified on real cars |
| Nissan, Infiniti (2007+) | Module scan with Nissan addresses |
| Ford, Mazda, Lincoln (2003+) | Engine, transmission, ABS. Body modules sit on MS-CAN and need an OBDLink MX+ |
| GM, Opel, Chevrolet, Cadillac (2004+) | Engine, transmission, ABS and GMLAN codes - added in 3.1.13, being verified on real cars |
| Mercedes-Benz, Smart (2004+) | Engine, transmission and modules found by ID-pair discovery - added in 3.1.13, being verified on real cars |
| Hyundai, Kia, Renault, Fiat, Chinese makes | Engine and standard modules |
| BMW, Mini | Generic engine data over ELM327. All modules and coding need a K+DCAN or ENET cable |
Three steps to your first report
- Install the adapter driver. USB units use a CH340, FTDI or PL2303 bridge and each has its own package. Bluetooth SPP units pair in Windows settings with PIN
1234or0000. WiFi units create their own network, usually at192.168.0.10on port35000. - Download and install Diagnost from the download page. Nothing else to configure.
- Plug the adapter in and switch the ignition to ON. The program walks the COM ports, paired Bluetooth devices, BLE peripherals and the WiFi endpoint, picks the one that is actually on a car, sorts out 38400 or 115200 baud, and starts scanning.
Test the adapter first, with nothing installed
Not sure the adapter you bought is any good? Open the in-browser check. It talks to an ELM327 over USB or BLE straight from Chrome or Edge and reads engine codes in seconds. For choosing between models and spotting a cut-down clone, see the full ELM327 guide.
How it differs from the usual options
Most ELM327 programs ask you to pick a COM port and a baud rate before they will do anything, then show generic OBD-II only. Diagnost removes both limits: automatic adapter discovery, and manufacturer module addresses on top of the standard. Against ScanMaster-ELM and OBD Auto Doctor the difference is module depth and price - Diagnost is free with nothing held back. Against phone apps such as Torque and Car Scanner it is screen space, trip recording, VIN history and support for cables no phone can use. And instead of printing a bare P0171, it tells you what to check first.
If the software does not see your adapter
- No COM port at all. The bridge driver is missing - look for the entry with a warning icon in Device Manager and install the package for that chip.
- Paired but not connected. Bluetooth pairing is not a connection. The SPP channel only opens while an application holds the outgoing port; remove and re-pair if it refuses.
- Adapter found, car silent. Ignition must be ON rather than accessory. If it is still silent, the adapter is a cut-down clone or the bus is not on pins 6 and 14.
- WiFi joined, no data. Make sure Windows has not jumped back to a network that has internet.
Requirements
- Windows 7, 8, 10 or 11. macOS is also listed for USB and WiFi adapters. There is no Android or iOS version.
- Any ELM327 - USB, Bluetooth SPP, BLE or WiFi. OBDLink works too, as does a J2534 pass-through device (support added in 3.1.12, still being verified on real devices).
- The USB bridge driver for USB models: CH340, FTDI or PL2303.
- For BMW: a K+DCAN cable for E series or an ENET cable for F, G and I, about $10 each, plus the EDIABAS package from the download page.
Questions and answers
Is there free ELM327 software that reads ABS and airbag?
Diagnost is free, has no ads and no unlock keys, and it does read ABS, transmission and airbag modules on CAN-bus cars. It does that by sending manufacturer UDS and KWP requests to module addresses, which is beyond what the generic OBD-II standard covers.
What is the best ELM327 software for Windows?
It depends on what you need. For generic engine data almost anything works. The differences show up in module coverage, whether the software finds the adapter for you, and whether it explains a code or just prints it.
How do I connect an ELM327 to a Windows laptop?
Install the driver for the USB bridge inside the adapter (CH340, FTDI or PL2303), or pair a Bluetooth unit with PIN 1234 or 0000, or join the WiFi network the adapter creates. Then plug it into the OBD-II socket, turn the ignition to ON and start the software.
Which COM port and baud rate do I select?
None, if the software does its job. Diagnost enumerates COM ports, paired Bluetooth devices, BLE peripherals and the WiFi endpoint, tries 38400 and 115200, and connects to whatever answers correctly.
Does ELM327 software work over Bluetooth on Windows 11?
Yes. Windows creates two virtual COM ports when you pair an SPP adapter and only the outgoing one carries traffic, which is the single most common setup mistake. BLE adapters skip the virtual port entirely and are connected directly.
Will it work with my cheap clone adapter?
Almost certainly, because every ELM327 on sale is a clone - the original chip was discontinued in 2022. Adapters sold as v1.5 are usually complete; cut-down boards labeled v2.1 will read engine codes but drop out on longer module replies.
Can PC software do more than a phone app?
A laptop gives you a screen wide enough for multi-sensor graphs, trip recording, session history per VIN with a diff against the previous visit, and module backups. It also lets you use BMW K+DCAN and ENET cables, which no phone can drive.
Does the software need an internet connection?
Scanning modules, reading codes and watching live data all work offline. A connection is only needed for the built-in AI mechanic that interprets what the modules reported.
Download Diagnost
Free program: scans every module on any make, live data, service functions and an AI mechanic built in. Finds the connected adapter on its own and picks the one that is on the car.
The program for other adapters and makes
Updated: 2026-09-05