December 29

How to clear obd2 codes with or without a scanner

The sight of the “check engine” light is the last thing every car owner wants to see. Knowing the exact cause of why it appears is crucial as it will eventually save you money and bring you a great sense of relief. Fortunately, you do not need to hire a mechanic to your car and find out what is wrong and can instead decide to make use of the onboard diagnostic scanner (OBD2). With scanners, you can get to carry out your vehicle’s maintenance handily, thereby safeguard yourself from experiencing any mechanical damage while on the road. However, whereas using an OBD2 scanner is simple, some people usually find it somewhat confusing. In this article, you will be taken through how to clear OBD codes with or without a scanner. Subsequently, you will never experience an issue that you cannot be in a position to solve, and this is essential in case your car spoils during the night or in the middle of nowhere; hence have concerns about your safety.

How do you clear OBD2 codes without using a scanner?

Clearing OBD2 codes without making use of the scanner is easy, and you can do this in a few steps. Nevertheless, before you even decide to do that, you need first to know what the check engine light means as it usually shows numerous faults with your vehicle. Some of the issues highlighted by the check engine light include automatic transmission, airbags (SRS) as well as anti-lock brakes (ABS). Additionally, if you own an older model vehicle, the check engine light could mean a simple problem, for instance, a leaking gas cap to a complex issue such as transmission or emission problems.

So what do you do if you do not have your OBD2 scanner with you? Well, you need not worry as you can clear the OBD2 codes without making use of a scanner because the sight of the check engine light is very annoying. Nonetheless, removing the OBD2 codes without using a scanner is not always the solution because, in some cases, the check engine light switches back on after turning it off, especially if your car is experiencing a severe issue.

Therefore, here are the steps you need to take to clear the OBD2 codes in your vehicle. If the check engine light keeps turning back on after switching it off, you need to get the engine checked, as this is an indication, there is a serious underlying issue.

Here are the steps you need to follow to clear OBD2 codes without necessitating to use a scanner;

  • Park your vehicle in a safe and level ground. After that, hold its parking brake and then open the hood.
  • Detach the negative black cable from the car’s battery, and if it has been tightened firmly, you need to use a wrench to make the battery terminals clamps lose.
  • Repeat the previous step with the positive red cable, and you need to take extreme caution to ensure the positive and negative candles do not get into contact with each other.
  • After removing the cables from the batter, you need to then cycle the ignition switch ON and OFF, for three to five times.
  • Press your steering wheel’s horn button and sustain this pressure for between 30 seconds to one minute to drain all the power that is stored in the ECU capacitor. The horn is usually connected to the hot circuit, hence why it can be engaged in the ignition’s key position. Thus, by continually pressing the horn, you aim to drain out all the electrical power found in the ECU, with the battery still disconnected.
  • Whereas this step is optional, you should do it, and it entails you waiting for at least an additional 10 to 15 minutes before you reconnect the car’s battery.
  • Connect back the black and red cable to the battery. When doing this, you should start with the red one, followed by the black one. Once you do this, confirm the clamps have been attached to the terminals firmly.
  • Turn on the car and inspect whether the lights are showing on your car’s dashboard console. After the engine warms up, the check engine light should have turned off.

In case the check engine light is still open even with your engine turned on, it most likely means you did not drain the ECU completely. Thus, you need to repeat this procedure mentioned above and ensure you press on your car’s horn until you have fully drained all the power from the ECU.

Furthermore, unplugging your car battery to clear the OBD2 codes is not enough despite this technique working when clearing the OBD1 codes in older generation vehicles. However, for cars manufactured from 1996 going forward, you will be expected to follow the above-discussed process.

If the check engine light turns back on within a day after you cleared the OBD2 codes, you need to take this as a warning that your car requires to be inspected as this could mean a more serious underlying issue.

How to read OBD2 codes without a scan tool?

Make use of ignition keys

You can use your ignition keys to retrieve OBD2 codes, and all you need to do is turning the key and off without turning on the engine. Furthermore, you need to repeat this process several times, and this usually depends on the make of your car, but on average, it needs to be done five times.

Using an odometer

The odometer is another way you can get OBD2 codes without needing a scan tool. All you are required to do is to depress your car’s odometer and then simultaneously turn the car’s ignition key on and off. While doing this, you need to release the respective “trip” and “reset” buttons.

How to tell if OBD codes have been cleared?

Is there a way you can know whether the check engine light in your car has been cleared? Yes, there is, and all you need to use is a simple OBD2 scanner to know whether or not the check engine light has recently been reset.

However, before you know this, the first thing you need to figure out is how to reset the check engine light. This light is usually reset either by disconnecting your car’s battery or clearing the trouble codes using an OBD2 scanner. Both these techniques clear, albeit temporarily, every Diagnostic Trouble Code (DTCs) from the Onboard Diagnostic computer and resets the numerous systems in your vehicle to the Not Ready State. Typically, the check engine light comes back immediately or after two weeks, depending on the issue affecting your car.

Having understood this, you are now ready to know how to tell whether the check engine has been reset using an OBD2 code reader. Moreover, you need to confirm that the diagnostic tool can display I/M Monitor Readiness Status.

Here is a step by step guide on how to tell that the check engine lights have been reset;

1. Rotate the keys to the ON position without starting your vehicle.

2. Find the OBDII port below your car’s dashboard and then plug the OBD2 scanner.

3. Once the OBD2 scanner connects to the OBII port, it should power on. Subsequently, press Enter or Read on your scanner with this dependent on your scanner model.

4. Go down to the I/M Readiness menu and pick it.

5. Examine every system and if most of these say NOT READY, then know that the check engine light has recently been reset. The system usually reads one of the following;

OK/Ready: It means the On-Board Diagnostic is done with monitoring the system, and it has passed the assessment.

Pending/ Not Ready: This means the system monitoring is yet to be completed, so you should carry on driving your car.

Fail: OBDII has examined the system, and it has not passed, and a Diagnostic Trouble Code is often set. Consequently, the check engine light will turn on immediately or soon.

A vehicle that has ECU codes reset will have every system showing Pass/OK/Passed and, in some cases, a couple of Not Applicable if particular systems are yet to be installed. Nevertheless, if the codes have recently been reset, numerous emission monitoring systems often display Completed whereas others show Pending/Not Ready or even Fail.

Does disconnecting the battery reset the check engine light?

If you want to reset the check engine light, you can do it by simply disconnecting the battery. Doing this is just one of the several ways through which you can reset the check engine lights.

Can AutoZone clear codes?

Yes, AutoZone does clear codes, which is one of the various services they offer in diagnosing the check engine light. Subsequently, they provide you with a detailed printout of the troubleshooting code as well as the diagnosis, definition, and explanation of the possible issue plus the likely cause.

How far do you have to drive to reset the check engine light?

Once you are done clearing the computer, you should drive for about 100 miles to allow it to examine each sensor and then register the outcome closely. However, this sometimes can be completed after approximately 50 miles, and then you will have an idea of when to connect your OBD2 scanner and check the status.

How do you clear OBD2 codes with a scanner?

  • Connect the OBDII scanner to the diagnostic port of your car, and this is often found on the side of the driver, below the dashboard, and close to the steering wheel.
  • Switch on the OBD2 scanner.
  • Turn on your vehicle.
  • Wait for the scanner to start displaying the trouble codes and then press the “Clear” button to erase the codes.

How to use the Bluetooth OBD2 scanner?

  • Pair the OBD2 scanner to the selected inside the settings of the app to make sure it works.
  • You should then go ahead and restart the application.

What problems do you experience after resetting the OBD2 codes?

Whereas the process of resetting OBD2 codes is relatively straightforward, you still might experience a couple of small problems when you restart your vehicle. The reason for this is that you will need to drain all the ECU’s power to reset the codes successfully, and once the power has been restored, most of your car’s electronic settings will require to be rebooted. Thus, your radio, drive settings, as well as the clock, will most likely be reset.

Nonetheless, this should not be an issue of concern because your car typically needs to reset everything to the correct settings after draining the ECU. This entire process might take a minimum of one drive cycle, so you need not worry is not behaving as expected right away after turning it back on.

One of the most common issues you will encounter is with your car’s transmission. Therefore, because all of your car’s electronics are being reset, the shifting of the automatic transmission will not immediately reset everything as expected. Instead, you will need to take out your car for a drive before everything returns to normal.

Additionally, some vehicles feature an in-built mode that preserves your settings even after you completely drain the ECU of all its power. This is usually attainable using a memory gadget that separately stores the settings, hence safeguarding you always get a backup when necessary.

What should you do if the OBD2 codes turn back on?

After you reset your OBD2 codes without a scanner and the check engine light immediately comes back on, this could be an indication your car has a serious issue that needs an inspection by a professional. You should not take on the mentality that the check engine lights have been designed to annoy you, but to indicate instead that your vehicle needs to be checked out.

In such a scenario, it would be best you make use of an OBD2 scanner, which is available in a broad range and are relatively affordable. With these tools, you will be in a better position to know what exactly is the issue is affecting your vehicle before taking it to a mechanic.

How do you test an O2 sensor using an OBD2 scanner?

1. Connect your OBD2 scanner via the diagnostic link connector, which is usually triangular plus has 16 pins. You can easily find this in most vehicles, and if not, check out the internet or owner’s manual.

2. Connect the OBD2 scanner to your car.

3. Switch on the engine, not all the way, but only the ignition to allow for communication between the diagnostic tool and your vehicle.

4. Go to the menu section and pick “trouble codes” and then select the system you want to diagnose. Consequently, you will see various codes, that is, active and pending codes. Active codes usually show a problem within the system, whereas pending codes indicate a potential issue.

5. Diagnose the problem, depending on the code displayed. You can search these codes online and learn how to replace or repair the problem.

How to reset airbag light with an OBD2 scanner?

Before you even attempt to reset the light, you first need to inspect the trouble codes using a scanner. It is vital to reset an airbag light using a scanner to prevent the airbags from deploying.

To do this, you should inspect your vehicle’s monitoring system to see if there is any loose wire, and if this is not the issue, you should then proceed and examine the airbag clocking system. This system is usually located between the steering column and the steering wheel, with the clock spring responsible for airbag deployment, car horn as well as wheel-mounted buttons. Also, if the car horn is still faulty, it is a sign you need to have the steering wheel dismounted.


Having read through this article, you now have an idea of how to clear OBD2 codes without a scanner. Furthermore, you also have learned about the potential setbacks you might encounter during this process, among other essential details regarding your car’s engine and transmission system. Therefore, you are now better placed to do some of these repairs or replacements on your own and only hire a mechanic if the check engine light keeps showing. Eventually, you will end up not only saving money but also time going to the garage to have your vehicle checked.


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