How To Reset Car Computer Without Disconnecting Battery

When you try to start your car, but it fails to turn over, you might be tempted to disconnect the battery from your car to reset the engine control computer, this, however, will work on many cars and trucks, but it’s not always the best course of action

It is possible to reset your car computer without having to disconnect the battery, and this is what we will be talking about right below.

The method varies depending on what make and model of vehicle you drive, but there are two basic ways to reset the computer in a car that won’t start,  cars just turn off the ignition and restart it, others will require you to jumpstart the vehicle before continuing with the reset process.

What Is ECM In Car?

Ever wondered what an ECM in a car means? Well here is the answer just below.

An ECM is an electronic control module in a car system, it is the brain behind your car controlling virtually all the systems that make your car function properly.

It monitors most of the sensors in the engine bay to manage your vehicle’s air-fuel mixture and also regulates the emission control systems.

The ECM regulates four main parts of your vehicle’s operating system namely the idle speed, variable valve timing, ignition timing, and the air-fuel ratio.

It is responsible for making constant adjustments and ongoing adjustments to your engine, it shares vital data with the PCM and the TCM that controls the shifting, anti-clock brakes, and traction system.

What Does A Car Computer Do?

Your car’s computer is a collection of numerous electronic control units(ECUa) that communicate wirelessly with each other and other components on a network called an in-vehicle network(IVN).

These ECUs control many important functions in your vehicles such as anti-lock brakes, cruise control, and vehicle stability.

If one of these systems fails or malfunctions, it can cause serious problems for you and your passengers- and even put you at risk for injury and death. That’s why it’s so important to know how to reset your car computer if something goes wrong.

In most cases, you won’t need to take your car to a shop or use expensive diagnostic equipment, instead, you can reset it yourself using simple tools and techniques.

Here is what you need to know about resetting your computer.

Why your computer is acting weird might be either software or hardware issues. Hardware failures occur when parts wear out over time, but software errors are more likely to happen after recent software updates have been installed.

Software bugs are also more likely than hardware failures because developers are unable to test their codes fully before release. there wasn’t always a clear line between hardware and software issues, though, especially when they affect multiple devices on a network like your IVN. In these cases, it can be difficult to tell whether you need to replace a part or update your system’s firmware.

Symptoms of a Failing Car Computer

If you are experiencing any of these symptoms, you may need to reset your car’s computer. If it is malfunctioning, see a mechanic immediately.

Car computers can cause serious safety hazards when they fail, so don’t risk driving until you have identified and corrected any issues that arise from one improper vehicle diagnosis.

Some common auto issues are:

With newer cars, checking under the hood for problems can be difficult since most components are now hidden away behind plastic covers or in small compartments.

So before you open up anything, get familiar with where all of your car’s main components are located and what they look like this will help if something goes wrong while you are working on a repair job.

You should also know how to locate specific parts that could potentially cause issues such as the alternators, belts, spark, plugs, oxygen sensors, fuel injectors, and more.

For instance, if your car won’t start even after you have the plugs replaced, it may have been caused by a faulty ignition coil, or if it does at high speeds or when turning.

ALSO SEE: How To Program A Transmission Control Module

Tools Required to Reset Car Computer without Disconnecting Battery

A digital multimeter(or voltmeter) and a wire, or a paper clip. If you are going to buy a multimeter, I recommend getting one with auto-ranging as it makes life easier. Also remember it must be DC, voltage, and not AC.

Another option is a handheld computer scanner which usually has both functions: multimeter and scan tool in one device. It will save you time when diagnosing problems.

It’s also worth noting that these scanners can be used for other things than just cars such as testing power outlets and electronic motors/switches/ solenoids etc.

How To Reset A Car Computer

Sometimes your car computer or ECU becomes unresponsive and you need to reset it without disconnecting its battery.

If you are having trouble starting your car, try resetting your computer before you go out and purchase a new one. Here is how

  • Pullover to a safe place
  • Turn off your ignition
  • Open up your hood
  • Locate your fuse box
  • Unplug all your fuses for about 30 seconds(you can plug them back in after you startup)
  • Startup again, that should be able to fix the problem.

You might always want to have a mechanic check things out just in case.

How To Reset Car Computer Without Disconnecting Battery

There are several ways you can troubleshoot your car’s computer without disconnecting or removing it from your vehicle. The following is a step-by-step guide for how to reset a car computer without needing a professional service.

Before beginning, be sure to turn off your engine and remove any electrical devices that can cause interference with your computer. For instance, cell phones and mp3 players should be turned off before attempting to reset your car’s computer systems. Also, make sure all doors are closed and windows rolled up.

  • With your vehicle turned off locate your fuse box, it is usually located under your dashboard on either side of your steering wheel.
  • Locate the 10amp fuse labeled ignition
  • Remove the fuse and wait for 30 seconds before replacing it
  • Turn on your ignition key and allow 15 seconds for all electronics to boot up again
  • Try starting up the vehicle again.

How To Disconnect A Car Battery To Reset The Computer

If you are having trouble starting your car and think it may be a problem with your computer, you can rest it without disconnecting your battery.

Start by turning off all accessories such as headlights and power windows as these draw electricity from your battery even when they are not in use.

Next, turn on your hazard lights for five minutes, this will drain any remaining energy in your battery and restart your computer.

Once that is done, start your car again, if after that it still does not start then there is probably an issue with something other than your computer system. You should take your vehicle to a mechanic at that point.

How To Reset Car Computer Without Disconnecting Battery

How Long To Leave Battery Disconnected To Reset Car Computer?

The length of time needed depends on your make and model. You will find specific instructions in your owner’s manual but you should at least an hour and it may take up to 24 hours.

After that, reconnect your battery if you have a newer vehicle with electronics that require regular power from your battery, you may need to reset your clock before driving.

How To Reset a Car Computer Without a Scan Tool?

You can reset your car’s computer by disconnecting and reconnecting a set of terminals on your vehicle’s battery.

This is typically done when your car engine light turns on signaling a fault code in your car’s onboard computer, however many car drivers might not realize there are ways to reset an engine management system without having to remove a car battery.

How To Reset a Car Computer With a Scan Tool?

A scan tool can be used to access your vehicle’s onboard computer and also allow you to reset your car powertrain control module without having to disconnect your battery.

A scan tool lets you clear stored codes and troubleshoots problems and future problems that occur while driving.

The PCM controls all of your engine’s electronic functions including fuel injections, ignition timing, idle speed, and transmission shifting.

If any of these parts develop an ult, a code will be stored by your PCM so it can adjust itself according to when it senses a problem again.

If multiple codes are detected within a short period, some vehicles will disable certain components or even prevents you from starting the engine until they have been cleared using a scan tool or key combination at startup.

Will Touching Battery Cables Together Reset Computers?

Yes, it is an old mechanic trick for eliminating certain kinds of driveability problems.

Disconnect the battery ground cable for 10 seconds to reset the computer.

What it essentially does is erase all the stored fault codes in the PCMs, keep the memory alive, and turn the check engine light.

What Happens When the Ecu Is Unplugged?

What happens is that the car won’t run. An ECUs is the brain of the car. It controls everything including fuel injections and sparks.

Another danger is corrupting the PCM if there is static electricity.

However, if the ECU is unplugged it will retain any charge it may have previously.

Having the ECU unplugged itself will reset provided you leave it unplugged for at least 20-30 minutes, all power is supplied through the plug to the ECU.

How Many Miles Does the Car Need to Travel for a Car Computer to Reset?

About a 50 to 100-mile drive after clearing the car’s computer should be sufficient for your car’s computer system to monitor all the sensors and also register the results.

Drive the way and under the normal conditions, you are used to driving as the computer relearns all your driving patterns and conditions so it can adjust accordingly.

What Happens When the Car Is Running, and the Battery Is Disconnected?

It will cause a high voltage spike in the electrical system which is capable of damaging electronic modules or the charging systems.

It is, however, possible for a car to run without a battery as long as the alternator is large enough to handle all electrical demands.

Removing the battery while the car is still running is not a good idea. Your battery does more than just provide electricity, removing the battery from the circuits allows spikes and transients to travel around endangering every semiconductor circuit in your car.

Removing the battery burns out diodes in the alternator. Do not run your car engine without the battery, the alternator is usually not designed to handle a 100% load.

Does Disconnecting the Battery Stop the Check Engine Light?

Yes. Disconnecting the battery stops the check engine light and clears the error codes and also resets the engine light.

If you leave the battery disconnected for about 15minutes, the vehicle system will get completely reset when the battery gets reconnected.

What Does Resetting a Car Computer Do?

Resetting the car computer enables you to remove the long-term memory of the car’s computer memory.

The process helps in deleting error codes that are useful when conducting mechanical tests on your vehicle.

The data becomes idle with no record of natural and idle speed.

Resetting a car should not be done routinely, but should be when there are error codes and it should also be done where there is any form of modifications to the car that will most likely be felt by the ECU.

Drive the car normally, so the ECU can relearn the systems.

Does Disconnecting The Battery Reset The Ecu?

Yes, disconnecting the battery for 15 minutes will ensure there are no codes left behind and it will help reset the ECU.

There are diverse reasons why you might need to disconnect your car’s battery, but the top on the list is resetting the ECU.

Disconnecting the battery will help you clear the monitors and turn off the check engine light until the monitors relearn a new pattern through driving.

Will Disconnecting The Battery Reset The Car Computer?

Yes. Disconnecting the battery will reset the car computer and also stops the check engine light and clear the error codes and also reset the engine light.

If you leave the battery disconnected for about 15minutes, the vehicle system will get completely reset when the battery gets reconnected.

Can I Disconnect the Car Battery To Reset the Computer?

Yes, disconnecting the car battery will reset the computer of most cars.

However, it depends on the car model and ECU type. In some cars disconnecting the car’s battery will only reset the clock and radio precept but will not do anything else.

Disconnecting the battery will reset the car computer and also stops the check engine light and clear the error codes and also reset the engine light.

If you leave the battery disconnected for about 15minutes, the vehicle system will get completely reset when the battery gets reconnected.

Some problems you can face with disconnecting batteries include:

  • Damage to electronic modules
  • Drivability issues
  • Loss of air conditioning
  • False warning lights etc.

On any vehicle that has a computerized engine control, any slight loss of power to the powertrain control module will cause it to forget its adaptive memory settings.

Author: Mechanic Mike Besso

Hi There, I am Mike Besso and this website is dedicated to the automotive industry. I have been a mechanic for many years and my experience includes fifteen specialization in heavy commercial work as well as private cars. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked for a long time at Global Rebound Automotive companies (Toyota, TATA, BMW, Nissan, TVs, and Others ) as a Mechanic and Mechanics Supervisor. I hope to share some of my knowledge with others.

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