Quick Answer: Will Disconnecting Car Battery Harm Computer?

When disconnecting a car battery which one do you disconnect first?

Always work on the negative terminal before the positive when you disconnect your battery.

Grab a socket from your socket kit and hold it near, but not against, the nut on the negative terminal of your battery.

Ascertain visually the socket size you’ll need to loosen the nut..

What happens if you unplug the ECU?

However, if the ECU is unplugged, it will retain any charge it may have even if you create a power draw someplace else in the vehicle. So you’d need to wait a decent amount of time to be “sure” it’s drained. Some folks go so far as to unplug the battery and let the car sit over night.

Why is it necessary to remove the battery negative cable first before removing the positive cable?

Remove the negative terminal first. This very important. By doing this, you are disconnecting the battery from your car’s chassis. If you remove the positive terminal first and your metal tool makes contact with another metal part of the vehicle, you could cause a short in the system.

Which battery terminal Do I disconnect for storage?

The low-tech solution is to disconnect the negative battery cable. You’ll likely lose the stereo presets, time and other settings. If you want to keep those settings and ensure that your battery starts the moment you return, purchase a battery tender, also known as a trickle charger.

Does removing car battery reset ECU?

These trim values are stored in volatile memory, so removing the vehicle battery for a short while will reset them. … The car ECU maps aren’t held in volatile memory, so will not be affected by removing the battery. if it did, then your cars ECUs would all reset to factory every time the battery was removed.

What happens if you don’t disconnect the negative battery cable?

Never disconnect a battery cable when the engine is running. If the tool touches the battery positive terminal and a chassis ground simultaneously, as long as the negative battery cable is not connected, no damage will occur.

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

The readiness monitors will remain until the car has been driven long enough for the computer to evaluate the various system and sensors. The amount of time can vary based on the vehicle. In some cases it can take up to 100 miles for all of the computer monitors to completely reset.

What happens if you disconnect the positive terminal first?

It can fall across either terminal and the car and nothing will happen. If you disconnect the positive terminal first and you drop a spanner, it is possible for it to fall across the positive terminal and any earth on the car, with spectacular and possible dangerous results.

What does an ECU reset do?

“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.

Why do I have to disconnect the negative battery terminal first?

When a car is negatively earthed then it is prudent to take off the negative terminal first and connect it last. … The grounded terminal should be disconnected first to ensure that a battery dead-short does not occur, should the spanner disconnecting the other one contact a nearby grounded metal part.

Is disconnecting a car battery bad?

In order to disconnect the battery, all you have to do is remove the cable from the negative port. … If the cables do make contact or even get close, it could do a number of harmful things to your car, including frying your alternator, damage the cables, or worse, cause serious injury to yourself or others.

Is it OK to disconnect car battery overnight?

No, it won’t drain overnight if you disconnect the positive lead. However, it’s very bad practice & can be dangerous, assuming the car is negative earth/ground.

How long should I disconnect my car battery to reset computer?

Because some of the electrical current is preserved in the computer for a while afterward, most sources recommend leaving the battery disconnected for at least 15 minutes to make sure the computer forgets the code before you reconnect the battery.