If you purchased a car after 1996, it probably has an OBD-II port. But what is it for, and how do you diagnose errors with it?

If you purchased a car after 1996, chances are it has an OBD-II (Onboard diagnostics II) port. Every car or truck on the road manufactured after 1996 is legally mandated to have one installed.

OBD-II is an onboard computer that monitors emissions, mileage, speed, and other data about your car. It's connected to the Check Engine light, which illuminates when the computer detects a problem.

The OBD-II onboard computer features a 16-pin port under the driver's side dash. It allows a mechanic or anyone else to read the error code using a special scan tool.

Before OBD-I, each manufacturer had its own set of standards for OBD, meaning that mechanics had to buy expensive scan tools for each plug type. OBD-I was first introduced in 1987 and started the standardization of onboard diagnostics. It had sensors that detected emissions and minimized them through emissions-controlling valves. However, it had many problems and shortfalls.

As a result, in 1996, car manufacturers started to equip cars and trucks with an OBD-II port. Every system is mostly the same, but there are slight variations. These are known as protocols and are specific to vehicle manufacturers.

There are five basic signal protocols:

Pins 4 and 5 in all protocols are used for ground connections, and pin 16 is used for power from the car's battery.

Once the computer senses a problem with the engine or any other component of the car it's monitoring, it'll trigger the Check Engine light.

Diagnostic Trouble Codes (DTC) are stored in the computer system. Codes can vary from one manufacturer to another. However, anyone with an OBD-II scan tool can connect to the OBD-II port and read the diagnostic trouble codes from the computer.

Any OBD-II scan tool can read the codes because of the standardized pinout. Scan tools can read from any of the protocols listed above. The standardized pinout is as follows.

OBD-II scanners can connect to these ports on your vehicles and identify the trouble code from any manufacturer that uses one of the OBD-II protocols.

OBD-II scanners can connect to these ports and identify the trouble code from any manufacturer that uses one of the OBD-II protocols.

Traditionally, a mechanic would hook up a scan tool to the OBD-II port to read the DTC. Less expensive scanners would only provide a numeric code, which the mechanic would then look up from the manufacturer's manual or service website. More costly scanners will provide text error codes.

However, in recent years, there have been more advanced tools available for regular drivers who don't want to have to depend on a mechanic to find out what's wrong with their car.

One example is OBD-II scanners. These can come in an array of configurations like wired and wireless. You can also find devices that connect to your smartphone or laptop and some with their own screen. Whatever you prefer, the choice is there.

Another option is GPS trackers. These can be hardwired into your vehicle, though they are commonly placed in the OBD-II port to give the device adequate power. These can be especially helpful in keeping track of loved ones or young drivers.

The computer system in your car is constantly monitoring various systems and components throughout your car.

This means that any device plugs into the port can read the same information and pass it along to your mobile device. Imagine opening an app on your phone and viewing your vehicle's current fuel consumption, temperatures, oil pressures, and more.

It's possible today with any of the devices and apps listed below.

If you're looking for an inexpensive solution, you can't go wrong with this OBD-II diagnostic scanner for Android by Veepeak.

This device works with various Android apps like Torque Pro, Torque Lite, or OBD Car Doctor. Just enable Bluetooth, and you can view various sensor data and diagnose error codes when your Check Engine light turns on.

Unlike most other devices in this price range, this device also lets you clear the error codes for minor things like a loose fuel cap.

This wireless OBD reader by BAFX Products transforms your iOS device into an impressive, advanced OBD tool. Not only can you read all diagnostics data from your car, but you can also monitor real-time data like:

It's a useful tool to monitor data about your car systems that your dashboard doesn't show you.

However, keep in mind that the third-party apps that work with this device aren't free.

A slightly better device for your Android or iOS device is the Veepeak OBDCheck BLE with Bluetooth 4.0.

Just enable Bluetooth on your phone and connect to this scan tool to read information from your OBD-II port. The device can read all OBD-II protocols. You can use it with Torque Android software or even ScanMaster software for your Bluetooth-enabled laptop.

The BlueDriver Bluetooth Professional OBDII Scan Tool is for anyone who would like a more functional OBD-II port scanner. This scan tool is Bluetooth-enabled and works with both Android and iOS devices.

It's somewhat more expensive than other wireless port-readers on the market. However, it comes with the features you'd expect from the same expensive scan tools that mechanics use.

The device lets you use your mobile app to read and clear both basic and advanced error codes. It also includes advanced tests with live data, such as misfire counts, digital readouts, graphs, and repair reports from a frequently updated online database.

Reading and clearing error codes is useful, but if you really want to have access to real-time data, then the OBDLink MX+ OBD2 Bluetooth Scanner is the way to go. It's one of the more expensive options, but the features are simply amazing.

While the price sets this advanced scan tool within the range of many expensive tools mechanics use, its impressive features make it well worth the cost.

The OBD-II port has been available in vehicles for many years, but only recently has it been accessible to regular drivers. Having these devices and apps gives you much better insight into what's going on with your vehicle long before any significant problems ever occur.

Some port scanners also come with location tracking features. But if that's what you're more interested in, check out some of the best GPS trackers for your car. Even though they don't show you your car diagnostics, at least you can always find your vehicle as long as it has a GPS signal.

In addition, there are multiple uses for the OBD-II port that isn’t dedicated to just troubleshooting. You can also tune your vehicle with your OBD-II port, yielding more power and better fuel economy. The possibilities are endless!

We hope you like the items we recommend and discuss! MUO has affiliate and sponsored partnerships, so we receive a share of the revenue from some of your purchases. This won’t affect the price you pay and helps us offer the best product recommendations.

Based in the East Coast, Joshua Ko is an automotive writer. Graduating from The Pennsylvania State University, he spends most of his free time outdoors, writing, or in the garage.

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