ELM327 v1.5 or v2.1: the number means nothing, here is how to recognise a good adapter
Where these numbers come from
ELM327 is the name of a chip designed by a Canadian company, ELM Electronics, to translate the exchanges between a computer and a car's OBD2 port. This chip has had several official versions over the years, up to versions 2.x.
Adapters costing a few euros almost never contain this original chip. They use a common microcontroller, programmed with copied or rewritten software that imitates the ELM327. This software announces whatever version number its author chose:
- “v1.5”: as far as we know, there is no official version 1.5. This number comes from an old copy of the software, often installed on a PIC18F25K80 microcontroller. These clones generally handle most of the protocols.
- “v2.1”: the official version exists, but the clones that display it generally have rewritten, simpler software on a cheaper chip. Many do not handle all protocols (in particular those of older American cars) and ignore some commands, which disrupts the dialogue with some control units.
Conclusion: the number is mostly a clue, and it is itself imitated. A “v1.5” can be bad, and a branded adapter can answer “v2.1” or something else and work very well.
What the labels in the listings mean
| Label | What it means | What to make of it |
|---|---|---|
| “v1.5” | Software copied from the older generation | Rather a good clue, to be confirmed by testing |
| “v2.1” at a very low price | Simplified software, cheap chip | Be wary, especially for older cars |
| “PIC18F25K80” | Microcontroller used by the best clones | Rather a good sign, but impossible to check without opening the case, and sometimes false |
| “Dual board”, “dual chip” | Two circuit boards, often with the PIC chip | Same remark: a sales argument, not proof |
| “Compatible with all cars” | Nothing specific | Ignore it; only the protocols and your test count |
| “Reprogramming”, “coding” | Functions that modify the control units | Avoid them: DiagAuto AI does not reprogram anything, and these functions carry risks |
What the ATZ command returns
When connecting, an OBD2 app first sends the adapter the ATZ command (reset). An ELM327-type adapter answers with its identity, for example “ELM327 v1.5”. This is exactly the text that the listings copy, and that is why it proves nothing: it is written into the clone's software.
DiagAuto AI uses it for one thing only: checking that the device you are connected to really is an OBD2 adapter. A Bluetooth speaker or TV sometimes accepts the connection but does not answer: the app says so instead of reading codes “into the void”. If you want to see the raw answer, turn on “Technical details” in the settings: a “Send ATZ” button appears on the Diagnostics screen.
The test to run as soon as it arrives
Do it straight away, on your car, so that you can send the adapter back if it is not suitable. Plug it in (where is the port), switch the ignition on and connect it in DiagAuto AI.
- Read fault codes: the reading must complete, with or without a code. A “the car is not responding” message with the ignition on is a bad sign (protocol not handled or faulty adapter).
- Emissions checks: the list of ready / not ready tests should be displayed.
- Sensors: tick a few sensors (engine speed, coolant temperature, road speed) and start live monitoring with the engine running. The values should refresh regularly for several minutes, without disconnecting. The more sensors you tick, the slower the refresh: this is normal.
- Scan the control units (cars using CAN, generally since about 2008): the number of control units found gives a good idea of the quality. In our tests, a Wi‑Fi clone found only 2 control units on a BMW, where a better-quality adapter read 18.
- Disconnecting and reconnecting: switch the ignition off, switch it back on, reconnect. An adapter that needs to be unplugged every time will end up annoying you.
If steps 1 to 3 pass, the adapter is suitable for engine codes, emissions checks and sensors. Step 4 counts if you also want the inventory of the other control units.
The safest choice
If you have not bought one yet: an adapter from a well-known brand, sold by a reputable retailer, saves you this lottery. Allow €20 to €60 for a good model (observed prices, indicative). The list of models tested with the app is on the Which OBD2 adapter to choose page, and the detailed criteria are in our buying guide.
Frequently asked questions
My adapter answers “ELM327 v2.1”, should I throw it away?
No, test it first. If it reads your car's codes, emissions checks and sensors without disconnecting, it does the job for standard OBD2 use. It is mainly likely to show its limits on an older car or when scanning the other control units.
Is an expensive adapter necessarily better?
Not necessarily, but an adapter from a well-known brand, sold by a reputable retailer, is much less likely to be a poorly finished clone. What counts is the result of the test on your car, not the price or the number displayed.
Does the version displayed change anything for DiagAuto AI?
No. The app only checks that the device answers like an OBD2 adapter, then queries the car. What counts is the car's answers, and how the adapter passes them on.