OBD Dongles: What Are They?

These affordable tools pull back the curtain on your vehicle's inner workings.

OBD DonglesAustin Lott | Capital One

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Every modern automobile is equipped with an on-board diagnostic system or OBD. The OBD monitors vehicle systems on a continuous basis, and if there are any problems, it generates a diagnostic trouble code (DTC) that in some cases will cause the “Check Engine” light to illuminate on your dashboard.

In the past, it was necessary to purchase an OBD code scanner to read any DTCs saved by the monitoring system, or visit a garage or auto parts store to have the code read for you. Earlier versions, known as OBD-I, were more primitive and had fewer trouble codes. OBD-II is more sophisticated and is standard in most new vehicles. You can simply plug a small dongle into your vehicle’s OBD-II port, connect to it via Bluetooth, and then use an app to read each stored DTC.

In fact, OBD dongles and their associated software can do much more than just read codes. Here's everything you need to know about these dongles and how to use them.

What Is an OBD Dongle?

All cars and trucks built since 1996 have an OBD-II port installed inside the cabin. Typically, this port is under the dashboard on the driver's side (although mounting points can vary). An OBD dongle is a small, Bluetooth-capable device that plugs into the port and communicates with the OBD-II system. It is powered by the port itself and doesn't require any batteries or charging.

Some OBD-II dongles come with their own apps, but the majority will work with a long list of downloadable OBD-II scanning software available for both Android and iOS devices.

More Than Just Codes

OBD-II scanning apps are all capable of reading the DTC codes stored by your vehicle, and most will provide a brief explanation of what those codes mean. The majority of apps can also reset these codes, which you may want to do after a repair, or as a test to see if the issue recurs.

Codes are only the beginning of what OBD dongles have to offer. The OBD-II system also provides full access to the data collected by a long list of vehicle sensors, ranging from engine speed to intake manifold pressure to oil temperature. More sophisticated apps can connect to dongles and display this information on a virtual dashboard viewable on your phone, and even track things like fuel consumption and log other performance indicators over time.

How Much Does an OBD Dongle Cost?

OBD dongles are available with prices starting around $10, and topping out in the $250 range. Some of the more expensive dongles come with apps that provide a long list of functionality, including constant monitoring, push notifications to your phone, and maintenance scheduling. That said, it's possible to purchase a less expensive dongle and then match it with a modestly priced app such as Torque for Android or Car Scanner ELM OBD2 for iOS. That way, you can take advantage of most of what an OBD-II interface has to offer.

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Benjamin Hunting
Benjamin Hunting is a writer and podcast host who contributes to a number of newspapers, automotive magazines, and online publications. More than a decade into his career, he enjoys keeping the shiny side up during track days and always has one too many classic vehicle projects partially disassembled in his garage at any given time. Remember, if it's not leaking, it's probably empty.