Will disconnecting the battery reset ECU? Tips to know (2023)

Have you ever had the check engine light come on and not been sure what to do about it? A lot of people will take their car to a mechanic, but did you know that there are some things you can do to try and fix the problem yourself? In this article, we’re going to talk about how to reset your ECU by disconnecting the battery.


So, does disconnecting the battery on your car reset the ECU?

Well, unfortunately, there is no straightforward answer to this question. The fact of the matter is that there is no definitive way to know whether disconnecting the battery resets the ECU or not. This is because every car is different, and the ECU will respond differently depending on the make and model of the vehicle.

That being said, there are a few things that you can do to try and reset the ECU. You can try to disconnect the battery for some time – say, 10 or 15 minutes.

Another thing you can try is to disconnect the battery and then start the car up again. This would work on older cars.

It’s important to note that there is no guarantee that either of these methods will reset the ECU. It’s possible that they may not work at all.

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So, if you’re experiencing problems with your car and you think that the ECU might be responsible, it’s best to take it to a mechanic and have them look into it.

At the end of the day, whether or not disconnecting the battery resets the ECU is a bit of a mystery. However, there are a few things that you can try to see if it works for your car. If all else fails, take it to a mechanic and let them take a look at it.

Disconnecting the battery will reset the ECU of all car models?

The answer to this question is a bit complicated. In general, disconnecting and reconnecting the battery should reset the ECU in a car, especially for older car models.

However, there are some exceptions. For example, some newer models of cars have computer systems that are more complex and cannot be reset with this method.

Additionally, disconnecting and reconnecting the battery may not solve the problem if something is wrong with the ECU, or you have an error that needs to be checked.

If you are not sure whether or not disconnecting and reconnecting the battery will reset your ECU, it is best to consult with a mechanic.

They will be able to tell you if this method is likely to work in your car and, if not, may have other suggestions for solving ECU-related problems.

Does disconnecting the battery harm the ECU?

Disconnecting the battery can potentially cause damage to the ECU, but this will depend on some factors, such as the age and type of ECU and how long it is disconnected.

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If you are planning on disconnecting the battery, it’s best to consult your vehicle’s manual to find out whether or not there is any danger in doing so.

In most cases, it is best to avoid disconnecting the battery if possible, as there is always a risk of causing damage. However, if you do need to disconnect it for some reason, be sure to follow the instructions carefully. Some manufacturers forbid this action.

How long to keep the battery disconnected to reset the ECU.

The ECU (Electronic Control Unit) on your vehicle is responsible for a variety of tasks, from fuel delivery to ignition timing. When it comes time to reset the ECU, you’ll need to disconnect the battery for a certain amount of time.

How long you’ll need to keep the battery disconnected will vary depending on your make and model of car.

So, what battery terminal Do I disconnect first on the battery?

You’ll need to disconnect the battery for at least 10 minutes in most cases, and always disconnect the negative terminal of the battery first.

Some cars may require a longer disconnect time, so be sure to consult your car’s owner’s manual. If you don’t have the owner’s manual, always consult qualified personnel from a dealer. Once you know how long to keep the battery disconnected, go ahead and disconnect it.

Disconnecting the battery can be a bit of a hassle, but it’s worth it to reset the ECU. Once you’ve reconnected the battery, be sure to take your car for a test drive to ensure that everything is working properly.

(Video) How To Reset All ECU’s And Control Modules In Your Car Or Truck Safely

If you’re not sure how to reset the ECU on your car, consult a mechanic. They’ll be able to help you out.

Does disconnecting the battery also clear other error codes?

A few different error codes can occur on a car, and each one is typically related to a specific issue. In some cases, disconnecting the battery can clear these codes and help you troubleshoot the problem.

Some errors triggered are false, so simply disconnecting and reconnecting the battery will make the errors disappear from the dash because the ECU will recognize the problem as being fixed. However, if you scan the ECU with an OBD2, errors will most likely be stored in the memory

It’s also important to note that this isn’t always the case, so it’s best to consult your car’s manual to see if this is a recommended course of action for your specific vehicle.

If you’re unsure what to do, it’s always best to take it to a mechanic and let them take a look.

Does disconnecting the battery also cause the car’s audio player to reset?

Well, the answer to that question isn’t entirely clear, but in most cases yes, most experts seem to agree that disconnecting the battery will reset the audio player.

This is because the audio player relies on the car’s computer system to work, and when you disconnect the battery, that system is reset. Therefore, it’s likely that the audio player will also reset when you do this.

However, there are a few exceptions to this rule. For example, if your car has a built-in audio player, disconnecting the battery may not cause it to reset. In addition, if you have a portable audio player that is plugged into the car’s audio system, disconnecting the battery may not reset it either.

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So, if you’re having trouble with your car’s audio player, it’s a good idea to try disconnecting the battery. This may fix the problem, or make it worse if the audio players require a pin and you don’t know it and don’t have it, it will force you to pay a visit to a dealer and spend some money for the code.

Are there any other concerns to know if you want to disconnect the battery?

Yes, there are a few other things you should be aware of before disconnecting the battery. First, make sure that all devices and appliances are unplugged from the battery terminals.

Second, make sure that the terminals are free of any corrosion or dirt. If they are not, clean them off with a wire brush before disconnecting the battery.

Finally, always disconnect the negative terminal first and reconnect it last. If you connect the positive terminal first, it could spark or cause harm to the ECU.

So, those are some of the things you need to know before disconnecting a battery. Remember to unplug all devices from the terminals, clean off any corrosion or dirt, and disconnect the negative terminal first. Following these tips will help ensure a safe, successful battery disconnection.

Bottom line

If you have an older car with a check engine light that keeps coming on, or if your car just isn’t running right, try disconnecting the battery for a few minutes, it has a higher chance of success.

This may reset the ECU and clear any errors. Be sure to start your car again and drive it around a bit to see if the problem has been solved before taking it in for repair.


How long to reset ECU after disconnecting battery? ›

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?

Does disconnecting battery clear error codes? ›

Leaving the battery disconnected for a few minutes will ensure the vehicle systems will completely reset when you reconnect the battery. Secure the negative cable back to the terminal and cover it with the cap. Disconnecting the battery will clear the error codes and reset the check engine light.

How long does it take for an ECU to relearn? ›

You should leave your car's battery disconnected for a minimum of fifteen minutes and no longer than thirty minutes to reset an ECU.

Will disconnecting 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 many miles does it take for ECU 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.

What happens if you disconnect the positive terminal first? ›

If you disconnect the positive terminal first, one slip of your wrench could send a direct short to the ground, which can be very dangerous. Its possible that you could experience a huge spark, the wrench could melt in your hand or the battery could even explode!

Will disconnecting battery clear check engine? ›

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 code should be off.

Does clearing fault codes reset ECU? ›

Turning back the screw and erasing the codes is the same resetting the ecu.

How do you know if your ECU has gone? ›

The main symptoms of a faulty ECU

Well-known examples are: engine failure light (MIL light) that lights up on the instrument cluster, car that goes into emergency mode, the car shakes or when the engine no longer runs on all cylinders. It can all indicate a malfunction of the engine control unit.

How do I know if my ECU is working? ›

Here are the most common symptoms of a bad ECU:
  1. Check Engine Light stays on after resetting.
  2. Car was jump started on reverse polarity.
  3. Engine turning off for no reason.
  4. Water Damage or Fire Damage on the ECU.
  5. Apparent loss of spark.
  6. Apparent loss of injection pulse or fuel pump.
  7. Intermittent starting problems.
  8. Overheating ECU.

How do I know if my ECU is not working? ›

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.
Dec 15, 2020

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.

Is it OK to just disconnect the negative terminal? ›

It is not a problem.

The reason they say to remove the negative first is because it is safer for you. The negative cable in all modern cars is attached to the chassis of the car. SO when you put your wrench on the negative post to loosen it, and the wrench hits the chassis, nothing happens.

What does disconnecting the battery do? ›

Disconnecting a car battery helps prevent electrical systems like a clock or an onboard equipment/computer system from draining it. If a vehicle and its battery are left unattended for a long period, probably a month, then it might result in the damage of the battery and could even introduce the need for a replacement.

Can an OBD scanner reset ECU? ›

The Primary purpose of OBD Scanner is to provide data on Performance checks on the car - using data from engine and transmission and finding in faults. However - resetting ECU is not something which OBD Scanners are capable of.

Do I need to reset ECU after changing battery? ›

There is no need to reset the computer per say, but if you had any error codes that indicated a problem existed; then you'll need to have a professional mechanic complete a check engine light inspection.

How much does it cost to reset ECU? ›

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.

Can you reset ECU by pulling fuse? ›

Another way to reset your ECU system

Instead of opening your bonnet and removing the earth lead, you can also disconnect the battery from your car by pulling the fuse that powers up your radio or footlights. You can find this fuse near your fuse box, usually on the lower right hand side of your footlight controls.

Will disconnecting my car battery reset the computer? ›

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.

Do you disconnect positive or negative first when removing a car battery? ›

When disconnecting the cables from the old battery, disconnect the negative first, then the positive. Connect the new battery in the reverse order, positive then negative.” When you are replacing your car battery, It isn't always easy to remember the order in which to disconnect and reconnect the terminals.

Is it better to disconnect the positive or negative battery terminal? ›

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.

How long do I disconnect battery to reset check engine light? ›

Steps to Reset an Engine Light

It will have a black cap and a negative (–) symbol. Using a wrench, loosen the nut on the negative battery terminal and pull the negative connector from the battery. Keep it disconnected for 30 to 60 seconds.

What resets the check engine light? ›

To reset a check engine light without a scanner, disconnect the negative battery cable and wait a few moments. This will reset the diagnostic system in your vehicle, and if the underlying issue has indeed been resolved, the light should go off immediately.

What is hard reset in ECU? ›

In simple terms hard reset is equivalent to removal of battery (Power source) and connect it again. This implies that the memory (Volatile, Non-Volatile and Electronic sub components which directly connected to ECU, peripherals).

Does an ECU need to be reprogrammed? ›

When you install a new TCM in these vehicles, it must be programmed with dealer-level equipment or equivalent, and the programming must be performed on the vehicle. What's more, you should never try to drive the vehicle to the dealership after the repair; it may cause premature transmission failure.

Which service is indicate ECU reset? ›

The ECU Reset Service Identifier ( 0x11 ) is used by the client to request a server reset. To reset any ECU you need to connect your computer to the vehicle OBD-II port in the service station.

How do I test my ECU? ›

How do I test my ECU components? Identify which pins on the ECU connector correspond to the component. Set the multimeter to the ohms setting (resistance mode) and connect the leads. Check that the reading is within the expected range.

How do I know if my ECU is bricked? ›

How Do I Know if My ECU is Bricked? Its usually pretty easy (and quick) to identify if the ECU was bricked. If the ECU no longer responds to scantools after reflashing, then its bricked. If it looks like a brick.. and sounds like a brick.. then its a brick.

Can AutoZone test my ECM? ›

AutoZone offers Loan-A-Tool, Oil Recycling, Charging System Testing, Battery Charging, ECM Testing, Battery Testing, and Check Engine Light Fix Finder, all for free. Once you've received the results of your test you can decide whether or not you should replace your battery or have your car serviced.

Does ECU control everything? ›

The ECU controls everything in the engine, including the wheel speed, braking power, ignition timing, idle speed and the air/fuel mixture.

What causes ECM not to communicate? ›

The most common cause of a U0100 code is a faulty battery. If the voltage in your battery drops too low, it can affect network communications, which can cause your vehicle to come back with a U0100 code.

What is the most common failure of an ECM? ›

The most common source of ECM failure is in one of the wiring harnesses. If the wires to the transmission or fuel injectors become corroded, they can lose conductivity, leading to a failure. Fortunately, these issues can usually be resolved by replacing the corroded wires.

Can you tell if an ECM is bad? ›

Running diagnostics and testing your ECM is how you can rule out other issues and see if there is really something wrong with the engine control module itself. The first thing to do is test the ECM to see if it returns any error codes indicating a failure of a specific engine system.

How do I know if my ECM fuse is blown? ›

When the fuse blows, the engine control unit/module loses power and is unable to control the ignition process, the throttle (drive by wire) shuts and fuel ceases to be commanded to move. No spark is commanded to fire. In short, the engine dies and the car goes nowhere.

How long do you hold battery cables together to reset computer? ›

4) Connect the positive and negative battery cables together for approximately 5 minutes. This will drain all of the capacitors in the computers and forces them to cold reboot.

Which battery terminal must 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.

How do I disconnect battery to reset? ›

Disconnecting A Car Battery
  1. Start By Turning The Ignition Off. ...
  2. Find Your Car Battery's Negative Terminal. ...
  3. Loosen The Nut On The Negative Terminal With A Wrench. ...
  4. Remove The Negative Connector, Then Repeat With The Positive Terminal. ...
  5. Remove The Battery If Necessary.
Mar 25, 2021

Will disconnecting the battery stop a parasitic draw? ›

You can avoid parasitic drain on your battery by unplugging optional equipment such as cell phones and chargers when you park your vehicle for the night. You can also turn off every light in your vehicle and make sure that your trunk, glove box and doors are all fully closed and latched before leaving your vehicle.

What happens if you disconnect the negative first? ›

The negative () cable is the ground cable; it is always connected to the frame or body metal and can safely be disconnected first with no chance of causing sparks. By the same token, always reconnect the positive cable before connecting the negative cable.

What happens if I disconnect the negative battery terminal while car is running? ›

Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. The ECU, the speed sensitive steering, the memory seat adjustments, the cruise control, and even the car's stereo.

How long do you leave battery disconnected to reset ECU? ›

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.

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.

How long must you wait for ECUs to go into sleep mode? ›

Turn OFF all electrical loads, close and lock the doors, then wait for the ECUs to go into sleep mode. This may take anywhere from 10 minutes to 2 hours dependent upon which vehicle is being serviced and what equipment is installed in the vehicle.

How many miles do you have to drive after you disconnect your battery? ›

Drive 10-15 miles to allow the ECU to adapt and read data. If your check engine light comes on again, your car might be suffering from a severe issue.

How long do you have to wait after disconnecting battery? ›

Things You Should Know

Set aside 10-15 minutes to disconnect the battery, another 10-20 minutes if you need to remove corrosion, and another 10-15 minutes to put it back or install a new one. Reverse the original order and reconnect the positive terminal first, then the negative terminal.

What is ECU recovery mode? ›

If there is a problem uploading to the ECU, such as interrupt of vehicle power, then the ECU will be left in 'recovery mode'. In this mode the ECU will not run the engine, but can still be re-programmed or reflashed.

Does the ECU control timing? ›

Fundamentally, the engine ECU controls the injection of the fuel and, in petrol engines, the timing of the spark to ignite it. It determines the position of the engine's internals using a Crankshaft Position Sensor so that the injectors and ignition system are activated at precisely the correct time.

Will an ECM keep a car from starting? ›

Inability to start the vehicle

If the problem with the ECM is significant, the automobile may not even be able to start at all. A complete ECM failure means no engine management for the vehicle. As a result, the car is not able to start as it's missing core inputs from the computer.

How do I know if my drive cycle is complete? ›

Take your emissions test again after the scanner reads clear. After a few days of driving, plug the OBD-II back into the port and run another scan. If the error codes disappear and everything is green, you've confirmed that the drive cycle is complete and your car will pass the emissions test.

Can disconnecting battery mess up your car? ›

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!

Does disconnecting battery check alternator? ›

If you're tempted to test an alternator by disconnecting the negative battery cable, don't do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test.


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