Will Unhooking Battery Reset The Computer


Disconnecting the battery in a vehicle is often done for various reasons, such as performing maintenance or installing aftermarket components. In some cases, people wonder if unhooking the battery will reset the vehicle’s computer system. This article will examine the impacts of disconnecting the battery on the car’s computer and what you can expect when you reconnect it.

Important Outline

Understanding a Vehicle’s Computer System

Today’s vehicles are equipped with highly sophisticated computers, often called Electronic Control Modules (ECM) or Powertrain Control Modules (PCM). These computers control various aspects of the engine, transmission, and other systems in the vehicle. They also store essential information about the car’s performance, such as fuel efficiency and emissions.

Effects of Disconnecting the Battery on the Computer System

When you disconnect the battery, you are essentially cutting the power supply to the vehicle’s computer. This causes the computer to lose some of its temporary memory, including learned settings like idle speed, air-fuel mixture, acceleration, and transmission shift points. In most cases, these learned settings will be lost during battery disconnection, and the computer will revert to its default factory settings.

However, disconnecting the battery will not erase stored fault codes or “Check Engine” light warnings in the vehicle’s computer. These codes typically require a more specific procedure – either using an OBD-II scanner, or professional assistance is needed to clear the codes properly.

Reconnecting the Battery and the Vehicle’s Computer Reset

Upon reconnecting the battery, you may notice some temporary changes in how the vehicle operates. Since the computer has lost some learned settings, it may take a little time for the vehicle to relearn these settings. In some cases, the car might idle rough, or transmission shifts could be erratic initially. Usually, these issues resolve themselves within a few drive cycles as the computer relearns and adjusts to its optimal settings.

Additionally, be aware that disconnecting the battery may cause some vehicle systems to reset, such as the vehicle’s security system or radio codes. In such cases, you would need to consult your owner’s manual for the proper steps to reprogram these systems.

Alternative Methods for Resetting the Computer

If the goal is to reset the vehicle’s computer or clear stored codes, a better approach is to use an OBD-II scanner. These devices plug directly into the vehicle’s diagnostic port, allowing you to access the computer system and clear any stored fault codes or perform a full system reset. This method is much more reliable and accurate than simply disconnecting the battery.

In conclusion, while disconnecting the battery can cause some temporary changes in the vehicle’s computer system, it is not the most effective way to reset the computer. Using an OBD-II scanner and following proper reset procedures will ensure an accurate and reliable reset for your vehicle’s computer.

Step by Step Guide

To ensure a proper reset of your vehicle’s computer system when disconnecting and reconnecting the battery, follow these steps:

1. Locate the battery: Find the battery in your vehicle, which is often located in the engine compartment or under the trunk in some vehicles.

2. Turn off the engine: Make sure your vehicle is turned off and the key is removed from the ignition.

3. Disconnect the battery: Start by disconnecting the negative battery terminal first (usually marked with a “-“, black cable or black cap). Then, disconnect the positive battery terminal (usually marked with a “+”, red cable or red cap).

4. Wait: Allow the vehicle to sit for approximately 15-30 minutes to allow the computer system to lose temporary memory and reset to default settings.

5. Reconnect the battery: First, reconnect the positive battery terminal, followed by the negative battery terminal. Make sure the connections are secure and tightened.

6. Turn on the vehicle: Start the engine and let it idle for a few minutes to allow the computer to relearn its settings.

7. Test drive: Take the vehicle for a test drive to ensure everything is operating properly and to let the computer continue to relearn its settings.

Step by Step Guide With Bullet Points

– Locate the battery
– Turn off the engine
– Disconnect the battery (negative terminal first)
– Wait 15-30 minutes
– Reconnect the battery (positive terminal first)
– Turn on the vehicle and let it idle
– Test drive to ensure proper operation

Pros and Cons

Pros of disconnecting the battery to reset the computer:
– Inexpensive and doesn’t require specialized tools
– May fix minor issues by restoring default settings

Cons of disconnecting the battery to reset the computer:
– May not always be effective at clearing stored codes
– Potential loss of personalized settings
– May require reprogramming of security systems or radio codes


Q: How long do I need to wait before reconnecting the battery?
A: It is generally recommended to wait for 15-30 minutes to ensure the temporary memory is cleared and the computer system resets.

Q: Will disconnecting the battery erase my radio or security system codes?
A: Depending on the vehicle, disconnecting the battery may lead to the need to reprogram radio codes or security systems. Consult your owner’s manual for the proper reprogramming procedure.

Q: How can I ensure that I’m not accidentally causing damage to my vehicle’s electronics?
A: Before disconnecting the battery, make sure the vehicle is turned off and the key is removed from the ignition. Always start by disconnecting the negative terminal first to prevent electrical shorts.

Q: Will disconnecting the battery clear stored fault codes?
A: Disconnecting the battery may not be sufficient to clear stored fault codes in some cases. Using an OBD-II scanner is the most effective way to clear and reset the computer system.


While disconnecting the battery can lead to a temporary reset of the vehicle’s computer system, it is not the most reliable or efficient method. It is recommended that individuals utilize an OBD-II scanner to effectively diagnose and reset a vehicle’s computer. Furthermore, be aware of potential complications related to security systems or radio codes and consult your owner’s manual if such issues arise. Always follow safety procedures when disconnecting and reconnecting a battery to avoid damage to the vehicle or personal injury.

Leave a Comment