By editor on Apr 2, 2019

Diagnose Car Check Engine Light with your Phone

Turning your phone into an OBD2 scanner is easy. In less than five minutes you can troubleshoot your car yourself. You can read, clear, reset fault codes or monitor your engine performance with your smartphone with a help of an ELM327 Bluetooth adapter

In this article, we will show you how to use your iPhone or Android phone as a diagnostic scanner. If your check engine light is on, you will be able to know right away what the DTC code is, what it means and even reset it in seconds. There are many other benefits such as checking to see if the vehicle is ready to pass the emission test. 

What you will need 

  • iPhone or Android smartphone
    You already have this. 
  • Free OBD2 software
    There are many free Bluetooth OBD2 apps that you can download from the Apple Play or Google Play store. Two of our favorite apps are Torque Lite for Android or DashCommand for Apple. In this tutorial, we will be using Torque app but any free OBD2 Bluetooth app will allow you to diagnose your car and reset the check engine light. 
  • Bluetooth OBD2 Adapter - Average Cost $20
    A Bluetooth ELM327 adapter is probably the only piece you are missing. These OBD2 Bluetooth adapters have flooded the market and unfortunately, many of them are fake that fail to communicate with all vehicles

Turn your smartphone into an OBD2 car diagnostic scanner

These instructions work on all vehicles 1996 and newer including domestic makes such as Ford, Chrysler, GM; Asian makes such as Honda, Toyota, Subaru; Europen models such as Jaguar, Land Rover, BMW, Porche, VW, BMW, and Mercedes-Benz etc. 

Plug Bluetooth Adapter into the OBD2 port

The OBD2 port is located on the driver side under the dashboard. Typically it is near the hood release. Here is a couple of pictures on how the OBD2 port looks. 

car diagnostic using your phone and a obd2 bluetooth adapter

Turn on ignition

Turn the ignition until all the dashboard lights come on. This is position II. Don't turn on the car yet. 

install elm327 bluetooth obd scanner on andoird phone

Pair Bluetooth Adapter with your phone. 

On your smartphone go to Settings > Bluetooth and turn it on. Next, search for new devices. You will see the name of the Bluetooth adapter. It may show as OBDII, Vlink, Bluetooth ELM 327, BAFX, Kobra, BlueDriver or Scan Tool depending on the Bluetooth device that you purchased.   

Click on the name of the OBDII adapter and enter the pairing code. The pairing code should have been provided by the device manufacturer.

Enter pairing code.

If they didn't provide you with a code try 1234 or 0000. 

car code reader app torque plus bluetooth adapter

Scan vehicle for codes

Once the pairing is complete, allow the phone to connect to your vehicle's ECU. Click on read fault codes. If your check engine light is on, you will get a Diagnostic Trouble Code (often referred ad DTC or fault code) and a description of what it means. You can also monitor the readiness status to see if your vehicle is ready to pass the emission/smog test.

check emission smog test status using car diagnostic app for android or iphone

As you can see in this picture this vehicle is not ready for an emission test. Once you all the test change to Complete you will be able to take your car for emission testing and pass it. ;)

Using your phone to diagnose your car's Check Engine Light (CEL) and fault codes is easy and can save you money in the long run. An OBD2 Bluetooth adapter will also allow you to monitor your car sensor live and test to see if the vehicle is ready for emission testing.

Don't expect to diagnose ABS, Airbag or ESP light with a cheap OBD2 Bluetooth adapter. If you are buying an ELM327 adapter you won't be able to connect to any other system except the engine. Which is fine if you are looking to monitor the engine and clear that check engine light.

As the Bluetooth technology evolves we hope to see Bluetooth adapters be able to scan multiple vehicle systems. We are already seeing Bluetooth tools such as BlueDriver OBD-II Scan Tool being able to read and clear codes from ABS, Airbag, and transmission but this feature works only on GM, Ford, Chrysler, Toyota, BMW, and Mini. 

Car Diagnostic Apps

There are so many Bluetooth OBD car apps for both iPhone and Android devices. We wanted to share with you Top 5 most popular auto diagnostic OBD2 apps. 

OBD Car Doctor

  • Can display real-time sensor data. Can store diagnostics parameters from ECU for any OBD-II compliant car. Support data reading PID's from cars with 2 and more ECU.

Olivia Drive | OBD2 - ELM327

  • This obd2 APP is great for monitoring the ECU. Shows the basic required parameters:

1) Flow rate cars
2) Consumption
3) Spent fuel for the trip
4) Distance traveled per trip
5) Engine speed
6) Vehicle Speed
7) The temperature of the engine
8) Alternator voltage of the car
9) High speed
10) Torque

ScanMaster for ELM327

  • For all vehicle diagnostics to OBD-2/EOBD standards. Basically anything 1996 and newer. 


  • Allow you to setup dashboard, data monitor, setup gauges, check for fault codes and reset. Over 1 million installs and 4+ star rating. 

Torque OBD2 Diagnostic App

  • We have to admit this is the OBD2 app our staff uses. The Lite version is free and allows you save logs, monitor emission readiness, read, erase clear check engine light and a lot more. 
Benefits of using a Bluetooth adapter to diagnose your car?
  • Check Engine Light On 
    If your check engine lights came on, you don't need to go to your dealer (or mechanic) and pay over $100 for a simple diagnostic that you can easily perform yourself. Even if you don't plan on doing the repair yourself, it is to your benefit to know the cause of the problem. You can research the problem before you choose the repair shop that is going to fix your car. If the problem is just a loose gas cap, you can fix it yourself for free. 
  • Display live sensor data
    This is a list of sensor data that you can monitor live as your engine is running. 
    • Engine RPMs
    • Engine Coolant Temperature
    • Fuel System Monitoring
    • Show Vehicle Speed on your phone in case speedometer is broken. 
    • Long and Short Term Fuel Trim
    • Intake Manifold Pressure
    • Intake Air Temperature / Air Flow Rate
    • Timing Advance
    • Throttle Position
    • Oxygen O2 Sensor 
  • Check Emission Readiness Status
    You don't need to drive all the way to your inspection facility to know if your car will pass smog test or not. You can use your phone to know exactly when to take you car for an inspection. 
  • Vehicle Information
    You can retrieve the VIN number stored in the ECU using your phone. Just in case it doesn't match with the one printed on the vehicle sticker. 



Brandon, 2017-08-04

I got an kufung obd2 adaptor that said it would connect Bluetooth to my iPhone, but it will not let me connect when I try. Do you know the reason for this?

Ray, 2017-08-04

The kufung obd2 uses Bluetooth 4. Depending on which iPhone model you have it may only be Bluetooth 4 compatible. Try it with an Android device.

eddy kiyengo, 2017-09-06

its a great app
it works on my android device

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