How to Reset the Car Computer without Disconnecting the Battery

Cars nowadays come with complex electronic systems that are controlled by an onboard computer, also known as the Engine Control Module (ECM) or Powertrain Control Module (PCM). At times, you may need to reset the car computer to clear error codes, improve engine performance, or address other issues. Traditionally, this has been done by disconnecting the battery, but this method can lead to loss of presets and radio codes.

Here are the steps you need to follow to reset your car computer without disconnecting the battery:

  • Locate the OBD-II port
  • Connect the OBD-II scanner
  • Read and clear diagnostic trouble codes
  • Reset the car computer

In this guide, we’ll explore an alternative approach that allows you to maintain your settings while still effectively resetting your car’s computer.

Reasons for Resetting the Car Computer

Reasons for Resetting the Car Computer

You’ll know when you need to reset your car’s computer when it experiences any of the following problems.

1. Engine performance issues

Resetting your car’s computer can help when your vehicle is experiencing engine performance issues. The computer manages various aspects like fuel injection, ignition timing, and throttle response. If you notice a decrease in performance or fuel efficiency, resetting the car computer might restore the optimal settings and improve your car’s performance.

2. Check the engine light

When the check engine light comes on, it signals a problem with your car’s engine or emission system. After fixing the issue, resetting the car computer can help turn off the check engine light. It’s essential to first diagnose the problem and address it before attempting to reset the computer.

3. Emission system issues

Modern cars come with emission control systems designed to reduce harmful emissions. Sometimes, these systems can trigger error codes related to the exhaust system or sensors. Resetting the car computer can help clear these error codes and ensure your car’s emission system is functioning correctly. Keep in mind that it’s crucial to address the underlying problem before resetting the computer to avoid any further complications.

Tools Needed for the Reset

Make sure you prepare the following tools in order to reset your car’s battery without disconnecting the battery.

OBD-II scanner

An On-Board Diagnostics (OBD) scanner is a device used to read and clear diagnostic trouble codes (DTCs) from your car’s computer. OBD-II scanners are compatible with most vehicles manufactured since 1996. These scanners come in various types, from simple code readers to advanced diagnostic tools. For resetting the car computer, a basic OBD-II scanner should suffice.

The ignition key or push-button start

You’ll need your vehicle’s ignition key or push-button start to turn the vehicle on and off during the reset process. This is necessary for establishing communication between the OBD-II scanner and your car’s computer.

Step-by-Step Guide to Resetting the Car Computer

Step by Step Guide to Resetting the Car Computer

Now that you have the aforementioned tools on hand, let’s get started.

Step 1. Locate the OBD-II port

The OBD-II port is typically located under the dashboard on the driver’s side, near the steering column. In some vehicles, it may be behind a small panel or cover. If you have difficulty locating the port, consult your owner’s manual or search online for the specific location in your vehicle.

Step 2. Connect the OBD-II scanner

Once you’ve located the OBD-II port, plug the OBD-II scanner into it. Turn on your vehicle’s ignition or press the push-button start without starting the engine. This will power up the car’s computer and establish communication with the scanner.

Step 3. Read and clear Diagnostic Trouble Codes

After connecting the OBD-II scanner, follow the instructions on your scanner to read and clear any diagnostic trouble codes. It’s essential to note the codes before clearing them, as you may need to reference them later or share them with a mechanic if the issue persists. Clearing the codes without addressing the underlying problem may cause the issue to reappear.

When the scanner displays the diagnostic trouble codes, it will also provide a brief description of the issue. This information can help you understand the nature of the problem and guide you in taking the necessary steps to fix it.

Step 4. Reset the car computer

With the diagnostic trouble codes cleared, the car computer will automatically reset itself. Some OBD-II scanners may also have a specific reset function. If your scanner has this feature, follow the instructions on the scanner to reset the car computer.

After resetting the computer, turn off the ignition or push-button start and unplug the OBD-II scanner from the port. Start the engine and monitor your car’s performance to ensure the issues have been resolved. If the problem persists or the check engine light reappears, you may need to consult a mechanic for further assistance.

Alternative Methods

Don’t have an OBD-II scanner? Don’t worry! There are 2 alternative methods you can try to reset your car’s computer without disconnecting the battery!

Fuse box method

Another way to reset the car computer without disconnecting the battery is through the fuse box.

Locate the fuse box in your vehicle, usually found under the dashboard or in the engine compartment. Consult your owner’s manual for the exact location and the specific fuse associated with the car computer.

Once you’ve found the right fuse, turn off the vehicle and remove the fuse. Wait for approximately 30 seconds before reinserting the fuse.

This method can reset the car computer, but be cautious as removing the wrong fuse may cause other issues.

Brake pedal method

The brake pedal method is another option for resetting the car computer in some vehicles. Turn off your car and press down on the brake pedal.

While holding the brake pedal, turn on the headlights, and wait for about 30 seconds. Release the brake pedal and turn off the headlights. Start your vehicle to see if the car computer has reset.

Keep in mind that this method may not work for all vehicles, and it’s always best to consult your owner’s manual or a professional mechanic for guidance.


1. Can I reset the car computer by disconnecting the battery instead of using an OBD-II scanner?

Yes, you can reset the car’s computer by disconnecting the battery. However, this method can cause you to lose your presets and radio codes. Using an OBD-II scanner is a better option as it allows you to reset the car computer without losing any settings.

2. Will resetting the car computer fix all my engine issues?

Resetting the car computer may help resolve some engine issues, but it’s not a guaranteed fix for every problem. You should diagnose and address the underlying problem before resetting the computer to avoid further complications.

3. Do I need a professional mechanic to reset my car’s computer?

While a professional mechanic can reset your car computer, you can also do it yourself using an OBD-II scanner or alternative methods mentioned in this guide. Make sure to follow the instructions carefully and consult your owner’s manual for specific information about your vehicle.

4. How often should I reset my car computer?

There is no specific interval for resetting the car computer. It should only be done when there’s a problem with the engine or emission system, or when you’ve made modifications that require the computer to be reset.

5. Can resetting the car computer improve fuel efficiency?

In some cases, resetting the car computer can help improve fuel efficiency by restoring the optimal settings for your vehicle’s performance. However, it’s essential to address the root cause of the decreased fuel efficiency before resetting the computer.