Readers ask: When Changing A Car Computer Does It Matter If You Pull Just The Negatice Battery Cable?

Can you just unhook the negative battery terminal?

It’s a good idea to wear eye protection when working around batteries. First, unbolt the negative battery cable and disconnect it by lifting it free. It might take some wiggling and twisting to pull it off. Be sure never to let the wrench touch both the negative and positive terminals at the same time.

Which battery cable do I disconnect to reset computer?

Disconnect the negative battery cable and then the positive cable with a combination wrench. Clean the battery posts and terminals with the post and terminal cleaning tool, so you have a good connection when you’re done.

What happens when you disconnect the negative battery cable first?

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.

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Does disconnecting the battery reset the ECU?

How do you reset your car’s computer? Will disconnecting battery reset ECU? Can a ECU be reset? Yes, all ECU (Engine Control units) can be reset and be should reset once per manufacturer’s guideline for a smooth relearn process or upon installing a replacement unit.

Is it enough to disconnect negative terminal?

“If someone is going away for a few months over the winter, they should definitely disconnect the battery. It’s the only way to prevent battery drain,” Rashidi said. I would recommend taking the negative battery post out, and wrapping something around the end so it doesn’t touch anything while you’re not there.”

Why do you connect the positive terminal first?

Connect positive first, negative having less potential won’t arc. The higher the voltage, the greater the chance of arcing and fusion. On a car if negative first and you are touching any metal part of car, when attaching positive there is possibility of arcing through you. Your body becomes part of the circuit.

How long do I need to disconnect 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.

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

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.

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

When resetting the ECU it will take about 50km (31 miles) to relearn.

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

Expert Reply: By removing the negative battery cable you are disconnecting the battery from the chassis of your vehicle. If you begin to remove the positive side before the negative and your wrench would make contact with any part of the vehicle, then you could cause a short in the system.

What happens if you take the positive terminal off first?

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.

What happens if you only disconnect the positive terminal?

when the positive terminal is disconnected, it will arc when it comes into contact with just about any unpainted metal part of the car. The terminal doesn’t have to touch a metal part directly, it can (and will) go through metal tools (like a spanner, screwdriver or pliers).

What happens if you reset your ECU?

What does reset ECM refers to? Whenever you reset your ECM, then you remove the long term memory of the car’s computer memory. The process deletes error codes useful when conducting mechanical tests on your vehicle. The data becomes the default, and neutral and idle speed, spark, and fuel logs are no longer available.

What are the signs of a bad ECM?

Here are some telltale signs that indicate there’s a problem with the ECM:

  • Check Engine Light Starts Flashing.
  • Stalling or Misfiring Engine.
  • Engine Performance Issues.
  • Vehicle not starting.
  • Poor Fuel Efficiency.