The check engine light is crucial in knowing if your car has an issue. And for you to troubleshoot the problem, you need to read the check engine code so you can remedy the problem. And while the norm is to take your car to a repair shop for them to read your check engine codes, you can read them at home.
Keep reading to learn how to read ECU error codes without a scanner.
ProTip: OBDII code readers are dirt cheap and simple to use. If you know a thing or two about cars, grabbing a code reader and keeping it on your person will let you understand your car problems long before you drop it at a garage (or start tinkering with it)
Can you read codes if the check engine light is off?
Yes. Some codes are unrelated to the engine/emissions systems and don’t cause the check engine light to come on.
Can you read check engine light codes without a scanner?
Yes. You can read OBD2 codes without a scanner.
Here are other ways to retrieve the codes without a scanner;
Using the ignition key
The ignition key method is the easiest to obtain OBDI and OBDII codes. The user only needs to turn the key on and off without cranking the vehicle’s engine. Depending on the vehicle, this process must be repeated several times. Most vehicles require this to happen about five times; however, some require only three turns.
The process must be ended by keeping the key in the ignition but in the ‘ON’ position. If the engine is accidentally turned on, the process must start again. After the turns, the “check engine” or “service” light must be illuminated on the vehicle’s dashboard. Each pulse of light represents a specific number.
In a two-digit code, the pause indicates a separation of one digit from the next one. Codes will appear on the vehicle’s dashboard in this form; each code is a representation of a different meaning. The code definition, which can typically be found in the repair manual, will relate to the main problem with the vehicle.
Here’s a simple step-by-step guide:
Step 1: Turn the Ignition Key
Switch ON and OFF the ignition key without running the engine. Do this multiple times (3-5 times usually) and ensure you stop flipping your key in the ON position.
Your car model depends on the number of times you need to turn your ignition key.
Observe the dashboard behind your steering wheel, and if all lights there illuminate, you can stop turning the ignition key.
Note: If you accidentally crank the engine, don’t worry. Just start over, and your car will check for any saved check engine light codes.
Step 2: Check Your Dashboard
Right after the dash lights come up, they’ll turn off, except one—usually the service engine light. Now carefully observe it.
If you see the odometer displaying the engine light codes, note down every trouble code (DTC). This method usually works with newer vehicles or vehicles with the OBDII system.
However, if your check engine or service engine light begins to pulse or flash instead of the odometer display, your vehicle is OBD1. And the flash created by the engine light is your fault code.
How to read the code
Reading a code from a check engine light flash can be tricky.
Each engine light pulse represents a digit, and the pause between the pulse indicates the separation between the digits. A zero is represented with a quick engine light flash.
For example, vehicle fault Code 32 will go something like this:
pulse, pulse, pulse, PAUSE, pulse, pulse (3 and 2 = 32).
Step 3: Note and Interpret The Check Engine Codes
Note the check engine light codes as they flash. Then check your repair manual for code descriptions and understand the exact issue.
For example:
If you own a Honda, check engine code 0 implies an issue with the Electronic Control Unit (ECU), and code 16 implies problems with fuel injectors.
If you own a Nissan, fault code 22 indicates a problem with the fuel pump and code 31 ECU.
Let’s check out the other method that doesn’t involve an engine code reader or DTC scanner.
Using an odometer
Making use of the odometer is another way to retrieve the OBD2 codes. First, the user is required to depress the vehicle’s odometer. (The “reset” and “trip” buttons must be reset as well.) Simultaneously, the vehicle’s ignition key must be turned on and off. Finally, the process must be ended with the ignition key turned on.
The odometer’s respective “reset” and “trip” buttons must then be released. The codes will then be available on the screen of the digital odometer. The screen will indicate the problem with your vehicle.
The odometer method lets you read a check engine light code without a scanner or code reader.
Here are the simple steps to follow;
Step 1: Odometer Reset
Press the odometer’s Trip and Reset buttons while turning the ignition key ON. After turning the key ON, release the odometer Reset and Trip buttons to check if the Diagnostic Trouble Code or DTC appears on the odometer display.
If the fault code shows up, you’ve succeeded in generating a Diagnostic Trouble Code without a code scanner. Note down every fault code and check your manual for the DTC definitions.
Step 2 : Odometer Reset and Multiple Ignition Key Flips (Optional)
In case the reset method doesn’t work, try again.
This time press the odometer Trip and Reset button and switch the ignition key ON, OFF, and then ON again.
It’s important to end the action in the ON position. Then release the odometer Trip and Reset buttons. Check the digital odometer screen; the trouble code should appear.
NOTE: if the error codes still don’t appear, this probably means your car doesn’t support OBDII codes.
In that case, try Step 3.
Step 3: Use A Paper Clip Or Jumper Wire
If your car supports OBD1 and doesn’t respond to the aforementioned method, there’s another way to get your engine code — using a paper clip or jumper wire.
First, ensure your car is turned off. Then find the OBD port (diagnostic connector) underneath the steering wheel. For the exact location, go through your owner’s manual.
You’ll notice two terminals on the diagnostic connector. Connect them with a paperclip or jumper wire. This’ll create a closed circuit.
Then turn the ignition to ON without cranking your vehicle, and the engine light will flash, showing your trouble code.
The flash will appear in the same manner as mentioned in the ignition key method — pulses and pauses.
Now that you know how to check engine light codes without a scanner for OBDI and OBDII codes let’s answer some related questions.
Can I use my phone as an OBD2 scanner?
Yes. Turn your smartphone into an OBD scan tool with a wireless transmitter and a free app. This will enable you to check engine light codes at home.
Items needed
- Free OBD2 software
- Android: Torque Lite
- Check Engine App
- Bluetooth OBD2 Adapter
Steps to follow
Note: These steps work on all vehicles 1996 and newer, including domestic makes such as Ford, Chrysler, and GM; Asian makes such as Honda, Toyota, and Subaru; European models such as Jaguar, Land Rover, BMW, Porsche, VW, BMW, and Mercedes-Benz, etc.
Plug Bluetooth Adapter into the OBD2 port
The OBD2 port is located on the driver’s side under the dashboard. Typically it is near the hood release.
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 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 OBDII, Vlink, Bluetooth ELM 327, BAFX, Carly, Kobra, BlueDriver, or Scan Tool, depending on the Bluetooth device purchased.
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. Next, click on read fault codes.
If your check engine light is on, you will get a Diagnostic Trouble Code (often referred to as DTC or fault code) and a description.
You can also monitor the readiness status to see if your vehicle is ready to pass the emission/smog test.
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 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 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.
List of Check Engine Light Apps
There are several Bluetooth OBD car apps for both iPhone and Android devices. These include;
OBD Car Doctor
It can display real-time sensor data. Can store diagnostics parameters from ECU for any OBD-II compliant car. Support data reading PIDs from cars with two and more ECU.
Olivia Drive | OBD2 – ELM327
This obd2 APP is great for monitoring the ECU. It shows the basic required parameters.
ScanMaster for ELM327
For all vehicle diagnostics to OBD-2/EOBD standards. Anything 1996 and newer.
Dash Command
Allow you to set up a 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 to save logs, monitor emission readiness, read, erase clear check engine lights, and more.
Check this too: What Will A Bad Crankshaft Position Sensor Do?
How do I turn off the check engine light without a scanner?
To reset a check engine light without a scanner, disconnect the negative battery cable and wait a few moments.
- Turn off the vehicle and open the hood.
- Locate the battery and negative terminal. It is black or has a minus (-) sign.
- Use a wrench to loosen the terminal, then hold the negative cable to the side for 30-60 seconds. Do not let cables touch.
- Ask a friend to hold down the horn to drain additional power.
- Reconnect the negative cable and put everything back in place.
This will reset the diagnostic system in your vehicle, and if the underlying issue has indeed been resolved, the light should go off immediately.
Alternatively, you can use the method below to turn off the check engine light without an OBDII scanner;
Turning the Ignition On and Off
Switching the ignition on and off is also one method of hard reset without disconnecting batteries. Put the keys in your ignition and turn on your ignition. And then off consecutively after a second in each step.