Why And How To Reset Car Computer- A Complete Guide (2023)

Why And How To Reset Car Computer- A Complete Guide (1)

Today’s vehicles rely on computers, engine control modules, or units (ECM/ECU) that monitor the sensors in the engine bay to enable the car to perform and function at its optimum.

The car computer is an essential component in your car and is often referred to as the car’s brain. It regulates several essential car functions to ensure the car runs efficiently. Some of the functions of the ECM include; checking the oxygen to fuel ratio, tracking idle speed, and controlling the variable valve timing and the ignition timing to increase power or fuel economy. If the engine control module or its related components encounters an issue, it can cause the vehicle’s functionality problems. In the worst-case scenario, this may be detrimental to your car’s functionality, making it unsafe to operate.

To avoid this risk and minimize the potential damage to your car, it is advisable to be on the lookout for the symptoms of a faulty ECM. To do this, you must be quite conversant with the symptoms of a failing system.

What are the symptoms of a failing car computer?

As we have highlighted, the car’s computer monitors several important functions in your car, and its failure could put you at significant risk. To curb this, you should always be alert while operating your vehicle and look for any tell-tale signs of your car’s ill health. The following are the main symptoms that could point to a failing car computer.

Difficulties while starting your car

A problematic car computer is likely to cause difficulties while stating the car. Sometimes, the car may even fail to start completely. This may be happening due to the failure of power reaching the car’s computer due to a blown a fuse or a wiring issue. However, if the entire module has failed, your vehicle will stall due to the lack of engine control.

(Video) Doing This Will Reset Your Car and Fix It for Free

An illuminated Check Engine Light

An illuminated check engine light may also serve as a warning sign for the driver. The check engine light turns on when the vehicle is switched on, but this is a simple test to ascertain that the bulb is functioning correctly. It is not supposed to light again unless the car’s computer has detected some trouble with the vehicle’s circuit or failed sensors. An illuminated check engine light should be an issue when the computer fails to record a problem with its components. Therefore, if you notice the light constantly staying on or being inconsistent, it is probably a good time to check your car for any issues.

Burning Smell

A burning smell in your vehicle is another symptom you should never ignore. The first rule is to inspect your ECM whenever you detect a burning smell or notice visible burn marks. Heat and overload can easily cause problems with the computer and the rest of your vehicle’s components.

Unstable Engine Behaviour

A damaged car computer can cause your engine to jerk, stall suddenly, or misfire provided your transmission is maintained, and your car has enough transmission fluid. This issue is unpredictable and varies in frequency and intensity.

Engine Issues

A malfunctioning car computer negatively affects vehicle performance, such as fuel settings. Your vehicle would experience decreased fuel economy, efficiency, and poor timing and acceleration.

What is the Solution for a Failed Car Computer?

When any of these issues arise, the car computer should report an error code that determines the source of the problem. Consult your trusted mechanic to read these error codes and to eliminate other potential causes of an illuminated check engine light.

Sometimes the check engine light may remain on even after configuring and repairing the car’s issues. In such a scenario, you must reset the car’s computer to erase the saved error codes.

Resetting your Faulty Car Computer

This step-by-step guide will come in handy should you reset your car computer without involving a mechanic or other professional. The reset should restore the ECM to its default settings and clear all car computer-related problems in your vehicles, such as computer codes or illuminated check engine lights.

(Video) How To Reset All ECU’s and Control Modules in your Car or Truck

You can use two methods for resetting your car’s computer. The first option is to turn off the car’s battery to break the circuit and erase all memory. On the other hand, you can go about the computer reset procedure with the car battery still on and attached to the car.

Resetting the Car Computer with the Battery Turned Off

For this procedure, you would need a battery wrench or pliers and a cable tie or insulating tape. You can also prepare a 10-watt resistor. Remember to turn off your car before commencing.

Using the battery wrench, remove the battery terminals and the battery from its compartment. This will effectively break the circuit, thus, preventing the flow of power into the engine.

Next, short the negative and positive wires of the engine, and tie them together using the cable tie or insulating tape.

Do the soft reset by leaving the wires short for about 45 minutes. This should drain the circuit of any residue current and cut the power from the car computer, thus clearing errors.

Clean the battery and its terminals using water and baking soda. Remove all rust, and rinse the battery after cleaning to clean off all the solutions.

After the 45-min wait, restore the battery and reconnect all the terminals.

(Video) How To Reset All ECU No Scanner No Tools Required

Once everything is ready, switch the car back on and inspect the check engine light. The issue should be solved, and the error codes will no longer appear. Your check engine light will work properly, and you’ll be ready to go.

Resetting the Car Computer with the Battery Turned On

You can also reset your car computer without disconnecting your car battery. The rest of this article will explain how to go about the process. To begin, you will require a fuse puller and a code reader. You could also use a pair of pliers instead of the fuse pullers.

You will need to locate the vehicle’s fuse box to go about this process. Please search for a cover detailing the car’s various fuses and corresponding amperage. Once you have found it, you can follow the rest of our steps. legit-earner

Remove the cover, and using the fuse puller or pliers, pull the fuses labeled “Back-up” with 7.5A. Locate another fuse labeled “ECU” and pull it out with 15A. Note that you will not have to disconnect the negative battery terminals for this procedure. The problem with following the former process and disconnecting the battery terminals is that you erase your entire car’s memory. This solves the issue with the check engine light and resets all other information in your vehicle, including the critical data.

Let the fuses remain disconnected for about 10 minutes, then reinstall them properly alongside the ECU.

Restore the fuse box cover and test your vehicle. You can drive for a few minutes to check if the check engine light issue has been solved. If the light stops illuminating, you are good to go.

If the check engine light comes on, reduce your speed and load as you drive. If available, maximize the built-in diagnostic services that report trouble codes. This will allow you to schedule a service appointment with your automaker.

(Video) Doing This Will RESET Your Car & Fix It For FREE

Why And How To Reset Car Computer- A Complete Guide (2)


The steps we have explained in our guide: How to reset car computer, have been tested by various drivers and car experts. You can, therefore, follow them to solve issues with your car’s computer effectively. The high chances are that resetting the computer will solve whatever issue you may have and get you back safely on the road. However, in case of any doubt in the process, you’d better seek a professional from an expert. That way, you can be sure that your car’s issues will be correctly diagnosed and configured.

Pay attention to the warning signs from your computer. Do not opt to wait for the symptoms to subside automatically. This is because the vehicle could keep performing poorly and deteriorating into an unsafe state for you and others on the road. A faulty car computer would cause little to no problems regarding safety, time, money, and other resources if addressed early enough. Consider your options well, especially when resetting your car computer.


How long does it take for a car computer to reset? ›

Here's something you probably don't know: after clearing the car's computer you will need to drive for about 50 to 100 miles. As you drive your car the computer will monitor all the sensors and register the results.

Should I reset my car computer? ›

Resetting your ECU is a popular myth. In reality, resetting your engine control unit (ECU) after modifying your engine isn't necessary. However, resetting your ECU can help you fix a faulty check engine light.

Do you have to reset car computer after replacing battery? ›

Most ECUs are self-learning and should reset themselves after learning that a new battery has been installed. If you're stuck, go to a mechanic for diagnostic assistance.

How much does a computer reset cost on a car? ›

The pricing for this can vary depending on the amount of work to fix it and the parts needed. Generally, this can be between $80 and $180. If you GPS continues to steer you of course and you end up stranded in a dark, creepy forest, it might be worth investing in a roadside assistance membership.

What happens if you master reset your car? ›

A master reset will erase all settings on your SYNC System such as navigated routes and the phone book for the sync system. By removing the nav chip or SD card, you're able to save this valuable information.

How do I know if my car has a computer problem? ›

Symptoms of Car Computer Damage
  1. Stalling and Misfiring. Early symptoms of car computer damage are stalling when idle and engine misfires. ...
  2. Apparent Loss of Ignition Pulse. ...
  3. Increased Mileage. ...
  4. Check Engine Warning Light. ...
  5. Electric Burning Smell. ...
  6. Car Won't Start. ...
  7. Loss of Acceleration.

Can Autozone reset car computer? ›

Option A: Go to Autozone

The answer is yes, but… there are a couple things to remember: Local auto parts stores will typically offer to read your codes for free, but not all locations will clear the light due to liability issues. Some of them don't even carry code readers that can reset the check engine light.

How do you complete a drive cycle? ›

15 minutes of steady driving on an expressway/highway followed by 20 minutes of stop-and-go driving with at least four 30-second idle periods. Allow the vehicle to sit for at least eight hours without starting the engine.

What is the purpose of ECU reset? ›

The main purpose of ECU reset is to recover the malfunction or not working condition or ECU hanged state, but it should able to communicate the external diagnostic system. At this point of time ECU/Server does not receive any request messages and also not respond to any messages.

Why would a car's computer need to be reprogrammed? ›

Flashing or reprogramming a car's computer is one way to keep the vehicle's engine control modules up to date. This is commonly done on vehicles 1996 and newer to make sure the microprocessors in the power train and fuel injectors are regulating the system properly.

Will disconnecting car battery reset everything? ›

On some older cars, disconnecting the battery will reset the system but in most new cars it does nothing, except potentially reset the clock and radio station presets.

How long should you unplug your battery to reset car computer? ›

You should leave your car's battery disconnected for a minimum of fifteen minutes and no longer than thirty minutes to reset an ECU. To disconnect a car battery, remove the negative power cable from the negative terminal of your car battery with the use of a socket or monkey wrench. What is this?

Which battery terminal do you take off to reset the computer? ›

Here's how to reset a check engine light manually:
  1. Turn off the ignition. ...
  2. Identify the negative battery terminal, which is usually marked by a black cap and a negative (–) symbol. ...
  3. Use a wrench to loosen the negative terminal bolt, and then take the negative cable and hold it aside.

Can you reprogram a car computer yourself? ›

You will need a reprogrammer. One end will be connected to a port near the steering wheel while another will be connected to a port on your computer. Your computer will download the new software that will be sent to the car. It will take about 30 minutes to reprogram the car, giving your car a new brain to work with.

What does flashing a car computer mean? ›

Reflashing or reprogramming is the process of replacing the existing software in a vehicle controller with new software. This requires an electronic transfer of approved calibration files from a vehicle manufacturer's website. You might think this service only includes vehicles under warranty.

What will happen if ECU reset? ›

"Resetting the ECU" is the process of clearing all the long term memory from the ECU's memory. These variables trim idle speed, fuel, spark, and more. The ECU will also store trouble codes for diagnostic capability.

How long does it take to master reset? ›

As a factory reset takes away all your data, it is essential to Backup before the process. It usually takes around 30 minutes to 3 hours to reset, depending on your device configuration.

Does a master reset delete everything? ›

A factory data reset erases your data from the phone. While data stored in your Google Account can be restored, all apps and their data will be uninstalled. To be ready to restore your data, make sure that it's in your Google Account.

Is it good to reset drivers? ›

Benefits of Resetting Your Graphics Driver

Restarting your graphics driver is a good place to start if you are having display issues as it is quick and easy and will likely fix your issue.

How can you tell if your ECU is damaged or faulty? ›

Lucas Auto Care lists the symptoms of a bad ECU below.
  1. Engine Lags or Surges. Because the ECU controls your engine's timing and fuel usage, you might notice engine performance issues such as lagging or surging in the module is going bad. ...
  2. Engine Misfires and Stalls. ...
  3. Your Car Won't Start. ...
  4. Check Engine Light Alert.
15 Dec 2020

What can a bad computer do to your car? ›

Erratic engine behavior may also indicate a bad or failing ECM. A faulty computer may cause the vehicle to intermittently stall or misfire. The symptoms might come and go and not appear to have any sort of pattern to their frequency or severity.

What controls the computer in a car? ›

An electronic control unit (ECU), also known as an electronic control module (ECM), is an embedded system in automotive electronics that controls one or more of the electrical systems or subsystems in a car or other motor vehicle.

How much does an ECU reset cost? ›

You should expect to pay between $150 and $300 at a local repair shop or service center just to have the ECU inspected and tested. In many cases, the faulty ECU can be repaired or reprogrammed, and this type of repair will usually run between $300 to $750, depending on the make and model of your vehicle.

How much does a dealership charge to program a ECM? ›

If the engine control module just needs to be tested, analyzed, and reprogrammed, it should cost you between $150 and $300.

Can Oreillys reset car computer? ›

If your vehicle is a 1996 or newer model year, head to your local O'Reilly Auto Parts store and ask a parts professional about a free Check Engine light diagnostic scan.

How many miles must be driven after reset? ›

In general, you will need to drive between 50-100 miles after you clear your car's computer. Hopefully, this will get rid of the check engine light once and for all. If it doesn't, there may be a more critical factor causing this item to turn on.

How long should a drive cycle take? ›

How Long does it Take to Complete a Drive Cycle. Preparation for it will take eight hours but, all in all, a basic drive cycle test should take around 30 minutes to complete, with about 20 minutes of actual driving. Understanding your vehicle's overall health can help you ensure it drives smooth and lasts long.

How long does it take a catalyst monitor to reset? ›

Idle vehicle for five minutes (to reach closed loop operation), then drive at a steady speed between 30 and 45 mph for two minutes. Toyota: The catalytic converter monitor will run after driving the vehicle at 40 to 55 mph for seven minutes, followed by driving at 35 to 45 mph for another seven minutes.

Does removing ECU fuse reset ECU? ›

Another way to reset your ECU system

Pull out your car's key. Pull out the fuse as well. Wait for 15 seconds and put it back in.

How long does it take to flash a car computer? ›

The reprogramming procedure usually takes 30-40 minutes.

How do I reset my car without a scan tool? ›

How to Reset the ECU/ECM Without Disconnecting the Battery:
  1. Pop the hood and locate the fuse box.
  2. Remove the fuse cover, then the ECU/ECM fuse.
  3. Leave the fuses for at least 10 seconds or up to 15 minutes.
  4. Reinstall the car computer fuse and replace the fuse cover.
  5. Take out your vehicle for a test drive.

What happens if you disconnect the positive terminal first? ›

It's important to disconnect the negative side of the battery first, otherwise you can cause an electrical short if the positive is removed first.

Does unplugging the battery reset the check engine light? ›

3) Disconnect the Battery then Reconnect

Ideally, this will clear the data, turning off the light. You can then reconnect the battery and turn the ignition on. After about a minute, the check engine light should be off.

What should you not disconnect when disconnecting a car battery? ›

You should never attempt to disconnect your car's battery while your car is powered on. We'd also recommend using safety equipment, like gloves and safety goggles, if you have them on hand.

What does resetting the BIOS battery do? ›

The BIOS (CMOS) battery stores persistent memory for BIOS and the Date/Time/Location settings for your console. Removing this battery and putting it back in will cause these features to reset to defaults. Unless otherwise altered by an end user, the BIOS settings on your console are also the default settings.

Which battery terminal should be disconnected first and why? ›

Removal of Old Battery

Remove the negative (-) terminal first. This precaution is necessary to avoid damage to wiring and the battery by accidentally grounding tools. Remove the positive (+) terminal.

Does disconnecting battery reset ECU? ›

Disconnecting your battery and draining the power to cause an ECU reset is one of the most common fixes for a check engine light that won't go away on its own. Doing so is equivalent to a hard reboot on a desktop computer, which is a standard way to eliminate many common problems.

How many miles does it take for ECU to reset? ›

If it was a longer period, then the car's ECU codes will usually change to emissions ready within 100 miles or so of driving after the ECU relearn's the car's sensors and characteristics.

How do you know if the computer in your car is bad? ›

Symptoms of Car Computer Damage
  1. Stalling and Misfiring. Early symptoms of car computer damage are stalling when idle and engine misfires. ...
  2. Apparent Loss of Ignition Pulse. ...
  3. Increased Mileage. ...
  4. Check Engine Warning Light. ...
  5. Electric Burning Smell. ...
  6. Car Won't Start. ...
  7. Loss of Acceleration.

How long do you need to disconnect car battery to reset computer? ›

You should leave your car's battery disconnected for a minimum of fifteen minutes and no longer than thirty minutes to reset an ECU. To disconnect a car battery, remove the negative power cable from the negative terminal of your car battery with the use of a socket or monkey wrench. What is this?

Which battery cable do I disconnect to reset computer? ›

Use a wrench to loosen the negative terminal bolt, and then take the negative cable and hold it aside. Keep it off of the battery for 30-60 seconds.

What happens to car computer when battery is disconnected? ›

Disconnecting or replacing a battery on a computer-equipped vehicle may cause starting, driveability and a number of other problems, including loss of air conditioning, power accessory functions (door windows, seats, sunroof), false warning lights, even damage to certain electronic modules!

What happens when you reset your system? ›

This reset option will reinstall Windows operating system and keeps your personal files, such as photos, music, videos or personal files. However, it will remove apps and drivers you installed, and also removes the changes you made to the settings.

What happens with system reset? ›

A factory data reset erases your data from the phone. While data stored in your Google Account can be restored, all apps and their data will be uninstalled.

Why does ECM need to be reprogrammed? ›

Reprogramming your ECM is necessary for keeping your vehicle control software up to date. Much like the operating system on your home computer, improvements in software are often made by your car's manufacturer. The software can be updated simply by downloading and installing the latest version.


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