Bluetooth OBD2 scanner: what it is for and how to diagnose your car

The amber engine warning light comes on in the dashboard and the questions start: is it serious? can I keep driving? how much will it cost to have it checked? Before going to the garage, you can find out for yourself what is wrong with your car using a Bluetooth OBD2 scanner and a free app. In this guide we explain what OBD2 is, what you can do with a scanner, how to use it with your phone and what it can do with an Android radio.

What is the OBD2 port?

OBD2 is the on-board diagnostics system fitted to all modern cars. The engine control unit continuously monitors sensors such as the lambda probe, the mass air flow sensor, temperature or turbo pressure and, when it detects a fault, stores a fault code (DTC) and, if it is important, switches on the engine warning light.

This data is read through the OBD2 connector, a 16-pin socket usually located under the steering wheel, near the fuse box or behind a cover in the centre console. In Europe it has been mandatory on all petrol and diesel cars for more than two decades, so yours most likely has one.

What can you do with a Bluetooth OBD2 scanner?

• Read fault codes and find out why the engine warning light has come on.
• Clear the codes and turn off the warning light once the problem has been fixed.
• See live data: revs, coolant temperature, turbo pressure, lambda probes, fuel consumption, battery voltage and much more.
• Check readiness for the roadworthiness test: see whether the emissions systems have completed their self-tests before the inspection.
• Check hybrid cars with dedicated apps, for example battery health.
• Check a used car before buying it: whether it has stored codes or whether someone has cleared them recently.

How to use it with your phone, step by step

1. Locate the car's OBD2 port, usually under the steering wheel.
2. Plug in the scanner with the ignition off. It needs no cables or setup.
3. Switch on the ignition or start the engine.
4. Install an app on your phone: Torque Lite (Android), Car Scanner ELM OBDII or OBD Fusion (iOS and Android) are among the most popular, and Dr. Prius for Toyota hybrids.
5. Connect via Bluetooth from the app and read the codes or open the live data dashboard.

The scanner supports the common protocols (ISO 9141-2, KWP2000, CAN-BUS, J1850), so it works with virtually any brand: Volkswagen, Seat, Skoda, Audi, BMW, Mercedes, Ford, Opel, Peugeot, Citroën, Renault, Dacia, Fiat, Toyota, Nissan, Hyundai, Kia, Honda, Mazda, Volvo and many more.

And with the car's Android radio?

Android radios let you install diagnostic apps such as Torque, and some can pair directly with a Bluetooth OBD2 scanner. That way you would have gauges for temperature, turbo pressure or voltage on the big dashboard screen, like an extra instrument cluster.

However, not all of them allow it: on many radios the Bluetooth module is designed only for the phone (calls, music and CarPlay or Android Auto) and does not pair with other devices. That is why we recommend using the scanner with your phone, which always works, and trying it with the radio as an extra. If you want to check with your unit, write to us and we will help you.

What an OBD2 scanner does not do

• It does not repair the fault: it tells you which system is failing so you can decide whether it is something simple or a trip to the garage.
• Clearing the code does not fix the problem: if the cause is still there, the light will come back on.
• Advanced brand-specific functions (coding modules, injector adaptation, ABS bleeding) require the manufacturer's own equipment or software.

Frequently asked questions

Can I leave the scanner plugged in all the time?
It is better to unplug it if the car is going to be parked for several days, because it draws a small amount of battery power.

Does it work on diesel cars?
Yes, it works on both petrol and diesel cars with an OBD2 port.

Does it work with iPhone?
Yes, it connects to iPhone and iPad with apps such as OBD Fusion or Car Scanner ELM OBDII, as well as Android phones and tablets.

Does it help me pass the roadworthiness test?
It lets you check before the inspection whether there are stored faults and whether the emissions monitors are ready, so there are no surprises.

My engine warning light has come on, can I keep driving?
If the light is steady and the car runs normally, you can usually get to the garage calmly. If it flashes or the car loses power, stop as soon as you can: it usually indicates a misfire that can damage the catalytic converter.

See the Bluetooth OBD2 diagnostic scanner

Check out the Bluetooth OBD2 diagnostic scanner to read and clear faults from your phone. And if you want to modernise your dashboard, find the CarPlay radio for your car in the catalogue by brand or see more add-ons in accessories.