Using your iPhone to diagnose your car’s check engine light

By , Mar 2, 2016

OBD Fusion Interfaces

All the do-it-yourself mechanics out there love being able to troubleshoot their own check engine light (CEL) to see what’s going on under the hood of their own cars. Typically, doing so requires an expensive OBD II scanner tool that plugs into the OBD II port underneath the dash.

But, with an app on your iPhone and a tiny accessory that plugs into the OBD II port, you could save some money and you’ll still have access to a lot of the information the scan tool would give you. In fact, because of how advanced your iPhone is, you may even get more information than a lot of the scan tools will offer.

In this review, we’ll be taking a look at the LELink Bluetooth Low Energy OBD II car diagnostic tool, which can be had for about $35 on Amazon, as well as the $9.99 OBD Fusion app, which can be had from the iOS App Store.

How does it work?

With a simple wireless dongle that plugs into the OBD II port underneath the dash of your car, you can create an access point where your iPhone can communicate with your car’s computer to receive data and statistics. The concept isn’t new, but the technology continues to mature and become more reliable as time goes by.


The LELink Bluetooth Low Energy OBD II car diagnostic tool is just one example of many dongles that do this, but after careful examination of customer reviews on Amazon, I selected this model because it seemed to be one of the best models out of the bunch with the highest amount of satisfied customers.


I would recommend a Bluetooth-style dongle over a Wi-Fi style one since the pairing is much simpler and the impact on the battery of your iPhone will be a lot less.

After you plug it in, the red light indicating that a power connection has been made should turn on, and now you can unlock your iPhone and power up the OBD Fusion app to start pairing the device to your iPhone. As you access it, green and yellow lights will flash to indicate data transfer between the devices.

Note: Although it’s a Bluetooth device, you do not pair it with your iPhone from the Bluetooth settings on your iPhone. Instead, you will launch the OBD Fusion app from your Home screen and connect to the dongle from the app.

Pairing the device with your iPhone

OBD Fusion Settings

From the OBD Fusion app, you can access settings that let you configure the behavior of the app. You’ll have to go to Settings > Preferences > Communications > Type and select “Bluetooth LE” from the list to work with this particular dongle. You would select the Wi-Fi option instead if you were using a Wi-Fi dongle.

Afterwards, you can then go back to the main interface of the ODB Fusion app, and proceed to connect with it. When you do, you’ll be able to configure your car by giving it a name, describing the vehicle by year, make, model, etc., and then you can configure your dashboard.

The OBD Fusion app

OBD Fusion Interfaces

The OBD Fusion app is incredibly useful. Here, you can access all of the statistics about your car.

The “Dashboards” section lets you see all of the gauges and live data in real time, including temperatures of your coolant and intake air, your vehicle’s RPM, speed, and manifold absolute pressure, and even your oxygen sensor readings. The types of gauges you use are completely at your discretion; you can add or remove any of them that you’d like, and even choose between a digital or radial readout.

The “Diagnostics” section lets you check your check engine light to see what’s wrong with your car. If the check engine light pops on, you can just plug this dongle into your OBD II port, launch this app, pair the devices, and check to see what code your car’s computer is throwing so you have some idea of what needs to be replaced to fix it. If there are no trouble codes, the app will be sure to let you now that everything’s okay.

Also useful is the “Maps” section, which allows you to track data related to where you’ve driven, and it even shows the speeds you drove while you were in specific locations. This location information isn’t shared with anyone but you, but is very cool because you can see where you use the most gas and where you’re the most fuel efficient.

Wrapping up

Overall, the $45 investment between the OBD II Bluetooth LE dongle and the App Store app seems to be a worthwhile alternative to the clunky and dated scanning computers that can be had for an arm and a leg at your local auto parts store. It’s really cool to see that you can use your smartphone to grab hold of this kind of data, and it’s a great way to ensure your car is in good health.

Would you use your iPhone to perform car diagnostics? Share in the comments.

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  • Chris Wagers

    Can you use this on multiple cars? I’m guessing yes but want to make sure before I buy it.

    • Vince Reedy

      Anything with OBDII port, which is mid 90s and up. High end cars may have limited functionality as far as clearing codes. It will help you diagnose problems and look at data and that’s about it. Good tool, saves taking it in to see what codes are stored in ECU.

      • Chris Wagers

        Thanks Vince! Do you know if it just the code numbers or tells you the actual code in simple language.

      • Vince Reedy

        It will give you the code number, a short description and provides a look up link to the web.

      • Chris Wagers

        Thanks again and now on to order!

      • Vince Reedy

        I may buy the bluetooth version since mine is wifi. I have to do code lookups separate because i am connected to the dongle’s wifi. Bluetooth would be much better.

      • Chris Wagers

        Sounds good. This will be my first. I’ve always wanted one but wasn’t sure which would be worth it. For the price and the article I’m taking the gamble. Thanks again Vince and Anthony!!

      • eqHullabaloo

        There is a setting in iOS that will use your mobile data connection if your wifi connection is slow. I don’t recall the name of the setting off the top of my head but if this is on you can still use the wifi based dongles and do the lookups at the same time without disconnecting from the wifi dongle.

      • Vince Reedy

        WiFi assist. I did not think of that. Thanks! I have mine disabled.

    • Yes, it can be used with multiple cars. You’d just need to set up separate car configurations in the app for each car.

      • Chris Wagers

        Thank you!

  • Ya

    Can you reset the CEL?

    • Robson Louro

      With certains apps, yes.

    • Yes, and some other apps will allow you to do this as well.

    • eqHullabaloo

      With the OBD Fusion app, yes you can reset the CEL. Standard disclaimer applies whenever resetting the check engine light though. All the smog monitors will be cleared/set back to not passed yet and other various side effects that apply regardless of what tool you use to reset the CEL. So if you are doing it because you need to pass smog you will have to drive the car enough to set the monitors again. At least with the OBD Fusion app you can view the state of all the monitors your car has so you know before you take it in if all the monitors are set/ready.

  • Todd Sorensen

    Will it work on a 2008 BMW?

    • Vince Reedy

      i have a 2006 and it lets you view information, but as far as resetting codes, you need a much more sophisticated setup. Google Ediabas, NCS Expert and INPA for your model. There are tutorials out there to do it if you are in to that sort of thing.

      • Todd Sorensen

        Thanks for the info Vince!

    • Yes, it should. Check to see if you have an OBD II port under your dash. If it does, it will work.

  • DOOManiac

    Or you can go to Autozone and they’ll tell you the code for free…

    • Vince Reedy

      Or you can have a tool at your disposal.

    • I’d much rather have a tool. The day my car won’t start, I’d rather check it myself than tow it to Autozone.

  • Robson Louro

    The IOS is now pairing with generic’s bluetooth dongle? 3 years ago i’ve had to chage all my monography to Android because there’s only connection thru wi-fi.
    Had to test again…..

    • Chris Wagers

      Yea I’ve seen trouble in the past where Bluetooth wouldn’t connect to certain things that android would. Hope so.

    • Yes, Bluetooth works on iPhone!

      • slamfest

        We know bluetooth works on iphone. What Robson is saying is valid. I have a bluetooth ODBII dongle and my iphone 6 will “not” connect to it. Android does just fine. Apple limits what bluetoooth it can connect to.

      • I was only trying to say that yes the Bluetooth dongle works with the iPhone.

        You don’t connect to it from the iPhone’s Bluetooth settings, despite common belief, but you connect to it from the app itself.

  • Joonyaboy

    Does it calculate fuel mileage if your car doesn’t have that readout?

    • It does calculate fuel mileage based on fuel consumption and distance traveled.

    • Morgan Freeman

      Most OBD apps will do that, yes. A calculator works just as well though.

      • Joonyaboy

        I was curious more about on-the-fly reading, so if I am cruising I can figure out the most fuel-efficient MPH. My old Ford Taurus had that on the dash

      • Morgan Freeman

        Oh yeah, I get ya. Should be able to set that up. You’ll need to know, or approximate, the weight of your vehicle and know the fuel capacity. One tip is to just display a vacuum gauge in whichever app you use and remember that higher vacuum should mean better economy. Reading that gauge might be easier anyways as any instantaneous economy numbers are generally irrelevant and can be pretty misleading.

  • triggerhappypunk

    is there any drain on the car battery if you keep it plugged into the OBDII port all the time (when the car is turned off)? i’ve got a decent OBDII port scanner that I bought from Amazon for under $20, reads and clears CEL codes. this bluetooth dongle sounds attractive if i can keep it plugged in constantly without killing the car battery.

    • Morgan Freeman

      It should draw very little power. I have quite a few things in my vehicle including an OBD bluetooth dongle and my overall parasitic draw is still within the manufacturer’s spec.

    • Yes, although I’ve never seen a case where a Bluetooth model will drain your battery to the point of issues arising. Bluetooth is very energy efficient. From what I have heard, Wi-Fi models are more energy-hungry. I’ve left mine plugged in for days and never had a hard start or anything like that, so the battery drain can’t be too bad.

      • triggerhappypunk

        ok, thanks! i work from home and only drive the car maybe once or twice every couple of weeks. good information, i’ll check it out. worse case if i find too much of a drain, then i’ll just install it in the wife’s car which is driven almost every day.

  • Yes, very similar, only significantly less expensive!

  • iByron

    If you already have a “smart car” dongle like Automatic, OBD Fusion will work with that, too!

  • Mark S

    Uhh OBD 2 scanners can be had for as little as $20. Don’t know why you think they’re expensive?

    • Looking at the selection, I’ve found that the cheaper ones do a lot less than the $100 ones.