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How to Reset Car Computer without Disconnecting Battery

How To Reset Car Computer Without Disconnecting Battery
Written by Nick Steiner

Resetting the computer for your car will erase the program codes. If the computer is faulty or failing, you will experience performance problems within the car.

It is actually easy for anyone to reset the engine control module without the need for expert knowledge and technology.

Symptoms of a Failing Car Computer

Symptoms of a Failing Car Computer

1. Car won’t start

Your car will have an air-to-fuel ratio. If there is a problem with the ECM the car will get the incorrect ratio. Your car might need to have the car turned several times before it will click over.

You may also experience hiccups when the car starts. If the ECM has already failed, the car won’t start.

2. Engine light is on

When the check engine light comes on, you’re dealing with a bigger problem, likely due to your ECM. You may experience other symptoms that can indicate an ECM issue.

3. Engine misfires

The wrong ratio of fuel to air can also cause your engine to misfire. A lean ratio will fail to ignite.

You may also experience a misfire to stutter when you have an incorrectly adjusted engine timer. If so, your ECM is the problem.

4. Lack of fuel economy

This is a problem that won’t start slowly. All of a sudden, you will start to notice your gas mileage decrease.

If you notice your mileage plummeting over a week or so, the sensor in your ECM is likely the problem.

5. Lack of acceleration

The TCM needs a working ECM to function the acceleration properly.

The ECM works to control the throttle to give you smooth shifting in an automatic vehicle. The TCM controls the overall shifting function.

When the ECM is not working correctly, it cannot adjust the throttle correctly, resulting in jerking and less acceleration.

6. Engine shutting off

Another symptom of a car computer problem is the engine turning off. This will most likely happen when you have your car in idle.

When the car is idling, it lacks the momentum to ignore a slight hiccup; therefore, it shuts off.

7. Rough shifting

When there is a problem with the computer, you might end up with problems shifting due to the ECM sending irregular data to your car’s TCM.

This means the car doesn’t get the information to shift at the right time. You may experience clunking or a feeling of rough shifting.

How to Reset Car Computer Without Disconnecting Battery?

How to Reset Car Computer Without Disconnecting Battery

Resetting with battery turned off

Step 1

To do this, you need battery pliers or a wrench and insulting tape or ties. Make sure your car is turned off before you carry out any work.

Using the wrench or pliers, take off the terminals on the battery and take the battery out. This will create a break within the circuit which stops any power from getting into the engine.

Step 2

Now you need to short both positive and negative wires on the engine and secure them together with the ties or tape.

Leave the wires short for about 40 minutes which allows for a soft reset. The circuit will be drained of any current and power from the computer. This will help remove any errors on the computer.

Step 3

Use this time to clean the terminals and battery using baking soda and water.

Remove any rust and residue solution afterward.

Once the 45 minutes is up, you can put the battery back and hook up the terminals.

Step 4

Once you have done that, you need to turn the car back on. The check engine light should be gone, and any error codes will disappear.

Resetting the ECM With Your Battery Connected

You can do a reset of the computer with the battery still connected. To do this, you need a code reader and a fuse puller.

If you don’t have access to fuse pullers, good-quality pliers will do the job.

Step 1

You need to find the fuse box for the vehicle. It will be behind a cover and it shows various fuses and their amperage.

Step 2

Remove the fuse box cover and with your pliers, pull out the ones ECU and pull out with a 15A. Next, search for the fuse Back-Up and pull this with a 7.5A.

You won’t need to disconnect the terminals at all and the car’s memory will stay intact that way.

Step 3

Leave the fuses disconnected for minimum 10 minutes. After the time has passed, reinstall them along with the ECU. Put the fuse box cover back in place and then do a test run.

Step 4

Take your car for a drive and see if the engine light comes on.

If the light has disappeared, the problem is solved. If you are still seeing the light come on, lower your speed.

If this doesn’t work, you can try the above method with the battery plugged in. If neither works, you will need to seek advice from a professional.

How to Reset the Ford Vehicle Computer Without Disconnecting

Step 1

I am taking the Ford F150 model for example. Before proceeding, you can put or wrap a non-conducting object over the negative terminal to ensure safety. First, disconnect the negative terminal.

Step 2

While the battery is connected, you must connect the other side of the jumper wire to the positive terminal.

Step 3

Connect a negative cable to the remaining end of the wire. The negative cable should be unattached. Do not get into contact with the battery terminal.

Step 4

Wait for 5 to 10 minutes and disconnect the cords. Then reconnect the negative cable.

Step 5

Now switch off all the accessories. start the car and keep it idle for 5 to 10 minutes so that the engine gets familiar with the idling value.

Step 6

Go for a test drive to adjust the shifting points. Light acceleration is suggested while changing each gear.

How to Reset the Honda Vehicle Computer Without Disconnecting

Step 1

Locate and access the fuse box under the car’s hood. Open the tabs and remove the top cover.

Step 2

Disconnect both the 15A and 7.5A fuse by pulling out the fuses. In some models, these fuses may be labeled as “ECU” and “Back-up”.

Step 3

Wait for 10 minutes and reconnect the fuse.

Step 4

Start the car and wait for 5 minutes. After that, you can go for a test drive.

How to Reset the Toyota Vehicle Computer Without Disconnecting

Step 1

Find the ECU fuse by following the pamphlet guide. It is typically located underneath the steering column where you will find a fuse panel

Step 2

Disconnect the ECU fuse. You can do it by using nose pliers or fuse tools.

Step 3

Start the car and wait for a few minutes in an idle state.

Step 4

Connect the ECU fuse and go for a test drive.

Why Is It Best to Avoid Disconnecting the Battery?

Disconnecting the battery is an easy and common way to reset the car’s computer.

This may be true, but it isn’t the safest method for the car. Disconnecting the battery will cause problems for the computer, such as losing memory.

Preset items, radio stations, the car’s best air/fuel mixture, and the shift points will all be erased. You also run the risk of being locked out of the vehicle due to the anti-theft system.

Safety Tips When Resetting Your Car Computer

  • Wearing safety glasses and a face shield
  • Read the manual for safety precautions first
  • Protect your hands, face, and body with proper clothing
  • Always work in well-ventilated areas
  • Never get too close to the battery while charging or testing
  • Keep anything that sparks, flames, or other ignition sources from the battery as it can cause an explosion
  • Use caution if you are using metallic tools to prevent sparks and short circuits
  • Vent caps need to be kept tight
  • Keep children well away from cars during this process

FAQs

1. What Happens When the Ecu Is Unplugged?

Ans. All of the memory that has been stored will get cleared. The variables will lower the idle speed, spark, and fuel. The ECU also stores the error codes to help diagnose problems.

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

Ans. Once you have reset the car’s computer, you will need to travel for around 50 to 100 miles. As the car goes, the computer will take note of the sensors and work to reset the results.

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

Ans. If you have the car running already, then pulling off the terminals won’t stop the car. The car needs a spark to hit the combustion part to start. Once it has started, the car will remain running.

4. Does Disconnecting the Battery Stop the Check Engine Light?

Ans. The battery needs to be disconnected for a minimum of 15 minutes to make sure the computer systems reset completely. All error codes and check engine lights will be cleared.

About the author

Nick Steiner

Nick has been a car nut for his whole life as far as he can remember. His father was a car dealer who used to change and repair his cars himself. As a result, Nick had the opportunity to get around all sorts of cars and learned to get his hands dirty repairing vehicles from an early age.

Nick is a great fan of Japanese quality and German preciosity. His deep passion lies in older models that he believes have a flair that takes him back to his childhood. He also loves their durability and reliability when compared to the modern models.

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