How to Diagnose Check Engine Light with a Smartphone
Turning your phone into an OBD2 scanner is easy. You can troubleshoot your car in less than five minutes and check the engine light yourself. With the help of an ELM327 Bluetooth OBD-II adapter, you can read, clear, or reset fault codes or monitor your engine performance with your smartphone.
This article will show you how to use your iPhone or Android as a diagnostic scanner. If your check engine light is on, you will immediately know what the DTC code is and what it means, and you can 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
- Free OBD2 software
- Android: Torque Lite
- Apple: DashCommand
- Bluetooth OBD2 Adapter
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 and fail to communicate with all vehicles.
Procedure
These instructions work on all vehicles 1996 and newer, including domestic makes such as Ford, Chrysler, and GM; Asian makes such as Honda, Toyota, and Subaru; and European models such as Jaguar, Land Rover, BMW, Porche, VW, BMW, and Mercedes-Benz.
Plug the Bluetooth Adapter into the OBD2 port.
The OBD2 port is on the driver’s side under the dashboard, typically near the hood release.
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Turn on ignition
Turn the ignition until all the dashboard lights come on. This is position II. Don’t turn on the car yet.
Pair a 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. The Bluetooth device purchased may show OBDII, Vlink, Bluetooth ELM 327, BAFX, Carly, Kobra, BlueDriver, or Scan Tool.
Click on the name of the OBDII adapter and enter the pairing code. The device manufacturer should have provided the pairing code.
Enter the pairing code.
If they didn’t provide you with a code, try 1234 or 0000.
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 receive a Diagnostic Trouble Code (often referred to as a DTC or fault code) and a description of its meaning.
You can also monitor the readiness status to see if your vehicle is ready to pass the emission/smog test. As you can see in this picture, this vehicle is not prepared for an emission test. Once all the tests are changed to Complete, you will 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 it is ready for emission testing.
Don’t expect to diagnose the ABS, Airbag, or ESP light with a cheap OBD2 Bluetooth adapter. If you buy an ELM327 adapter, you won’t 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 Bluetooth technology evolves, we hope to see adapters able to scan multiple vehicle systems. We are already witnessing Bluetooth tools such as BlueDriver OBD-II Scan Tool able to read and clear codes from ABS, Airbag, and transmission, but this feature works only on GM, Ford, Chrysler, Toyota, BMW, and Mini.
List of Check Engine Light Apps
There are so many Bluetooth OBD car apps for iPhone and Android devices. We wanted to share the top five most popular auto diagnostic OBD2 apps with you.
- It can display real-time sensor data, store diagnostic parameters from the ECU for any OBD-II-compliant car, and support data reading PIDs from cars with two or more ECUs.
- This obd2 APP is great for monitoring the ECU. Shows the basic required parameters.
- For all vehicle diagnostics to OBD-2/EOBD standards. Anything 1996 and newer.
- Allow you to set up a dashboard and data monitor, set up gauges, check for fault codes, and reset—over 1 million installs and 4+ star ratings.
- We have to admit this is the OBD2 app our staff uses. The Lite version is free and allows you to save logs, monitor emission readiness, read and erase clear check engine lights, and much more.
What are the benefits of using a Bluetooth adapter to diagnose your car?
- Check the Engine Light On
If your check engine lights come on, you don’t need to go to your dealer (our mechanic) and pay over $100 for a simple diagnostic that you can efficiently perform yourself. Even if you don’t plan on repairing yourself, knowing the cause of the problem is to your benefit. You can research the problem before choosing the repair shop to fix your car. If the problem is just a loose gas cap, you can fix it for free. - Display live sensor data
This list of sensor data you can monitor live as your engine runs.- Engine RPMs
- Engine Coolant Temperature
- Fuel System Monitoring
- Show Vehicle Speed on your phone in case the 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 to your inspection facility to know if your car will pass a smog test. You can use your phone to know exactly when to take your vehicle for an inspection. - Vehicle Information
You can retrieve the VIN stored in the ECU using your phone. Just in case it doesn’t match the one printed on the vehicle sticker.
