ELM327 Bluetooth Scan Tool Connectivity

ELM327 Bluetooth
ELM337 Bluetooth devices allow you to peel back the curtain to see exactly what your car's "brain" is thinking. alengo/E+/Getty Images

ELM327 Bluetooth devices provide an easy way to scan an OBD-II system for codes, read PIDs, and aid in diagnostics. These devices represent a low cost way for DIYers to tackle computer diagnostics, and they can even be useful to seasoned techs who find themselves away from their dedicated scan tools. However, there are a few ELM327 Bluetooth-related issues that you need to be aware of before you go out and buy one.

The most pervasive issue with ELM327 Bluetooth devices is that some low-cost scanners include unauthorized ELM327 microcontroller clones. These cloned chips often exhibit strange behaviors, but even legitimate hardware will fail to work with certain devices. If you want to use an iOS device as a scan tool, it's especially important to pay attention to these issues.

ELM327 Bluetooth Compatible Hardware

Scan tools that include an ELM327 microcontroller and a Bluetooth chip are capable of pairing with a wide variety of devices, but there are some important limitations. The primary devices you can use an ELM327 Bluetooth scan tool with are:

  • smartphones
  • tablets
  • laptops

The most convenient way to take advantage of ELM327 Bluetooth connectivity is to pair a scanner with a phone, but not all phones play nice with the technology. The primary exceptions include Apple iOS products like the iPhone, iPod Touch, and iPad.

The reason that iOS devices typically don't work with ELM327 scanners is due to the way that Apple handles the Bluetooth stack. Most generic ELM327 Bluetooth devices will fail to pair with Apple products, which means that Apple users are better off with USB and Wi-Fi ELM327 scanners. Jailbroken devices are a different matter, but there are a number of potential side effects and consequences with jailbreaking.

In some cases, other smartphones can also have issues pairing with certain ELM327 Bluetooth scanners. This is typically due to problems with unauthorized, cloned microcontrollers that don’t have up to date code.

Pairing ELM327 Bluetooth Devices

Aside from the situations outlined above, pairing ELM327 Bluetooth devices with smartphones, tablets, and PCs is typically a simple procedure. The most common steps are:

  1. Plug the ELM327 Bluetooth device into the OBD-II port
  2. Set the smartphone, tablet, or laptop to “scan” for available connections
  3. Select the ELM327 scan tool
  4. Input the pairing code

In most cases, the documentation that comes with an ELM327 Bluetooth scanner will include the pairing code and any special instructions that differ from that basic outline. If no documentation is included, some common codes include:

  • 0000
  • 1234
  • 6789
  • 9999

If those codes don’t work, other sequential sets of four numbers are sometimes used.

What to Do if Pairing Fails

If your ELM327 Bluetooth scanning device fails to pair with your smartphone, there are a number of potential causes. The first step you should take is to try alternate pairing codes. After that, you can try to pair the scanner with a different device. Some faulty cloned ELM327 microcontrollers have trouble connecting to certain devices, and you may find that your scanner pairs just fine with a laptop while it refuses to connect to your phone.

Another thing that can cause a failed pairing is the limited amount of time that your scanner remains discoverable. Most ELM327 Bluetooth scanners become discoverable as soon as you plug them in, but they stop being discoverable after a specific amount of time. If you make sure to perform the pairing operation within one minute of plugging the scan tool into the OBD-II jack, there shouldn’t be an issue.

If your scan tool still won’t pair, then you probably have a faulty unit. This is the primary reason that it’s a good idea to stay away from cheap, cloned scanners and to buy your scanner from a retailer that will stand behind defective products.

ELM327 Bluetooth Alternatives

The main alternatives to ELM327 Bluetooth scanners are devices that use Wi-Fi and USB connections. Wi-Fi ELM327 scanners are typically more expensive than devices that use Bluetooth, but they can be used with Apple products. Most USB ELM327 scanners aren’t designed for use with Apple products, but there are some Apple-authorized options that can be used with the dock connector.