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Reset Car Computer After Replacing Battery

Reset Car Computer After Replacing Car Battery

When you reset car computer after replacing battery you will be able to ensure that the replacements of car part you will be making in hopes to clear a check engine light, are completely required. Resetting car computer is one of the most common ways to do an ECM (Electronic Control Module) reset but what are its other implications and are there other ways to do it?

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Why is there a Need to Reset Car Computer After Replacing Battery


Although some individuals have the belief that the process to reset car computer after replacing battery in their car will solve the problem that their engine light is pertaining to, that is just not the case. The engine light is telling you that a sensor sent a message to the ECM (Engine Control Module) that it is out of specification thus needing to be tested. It may only be possible to erase the diagnostic trouble if you have already tested and really tried to fix the root of the problem as indicated by the Error Code.


But what if the Check Engine Light still comes on after the repair. If the check engine light is illuminated then there might be an electrical issue within the vehicle that must be fixed. But before replacing any of the car parts you will have to do an ECM reset to be absolutely sure that replacements are absolutely required. 


The easiest way to do this is with a scanner, but if you don't have one, simply disconnecting the batteries on many vehicles would suffice. Reset car computer after replacing battery to clear the error codes and reset the check engine light as well. In many cars, however, disconnecting the battery will delete not only diagnostic trouble codes, but also the security, the drivability, and the radio codes you need. So, before you disconnect the battery, look for any codes to make sure they're safe, as well as the drivability learning procedures.


Another reason to reset car computer after replacing battery is for the ECM to know the new parts when replacements are done and be able to store the data. This process should be done when any replacement parts are installed like a knock sensor or fuel filter,  even after some work on your car's air conditioning or diagnostics has been completed. If you need to replace your vehicle's ECM, you have to consult your maintenance manuals or the owner's manual to make sure everything is done as it should.


Every ECU (Engine Control units) can be reset and also should be reset at least once per manufacturer’s guideline so your vehicle can have a smooth relearning process upon installing a replacement component.

The Process to Reset Car Computer After Replacing Battery


So how do you go about the process to reset car computer after replacing battery. One method is to detach the battery cable for 2 to 3 minutes and then reconnect the battery and start the car and see if the check engine light comes back on.


Drive the car for at least 10 miles to let the ECU know there's a problem; if there is, the check engine light will come back on, and you can look at the fault code the ECM produces. These codes will lead you to the root of the issue, enabling you to begin removing parts in an effort to fix it.


After installing the new parts, you can continue to reset your computer so that the engine control can “learn” the new parts and store the new data. Before you reset the ECU, make sure there are no issues with the battery cables and that you have a backup power source.


Reset Car Computer After Replacing Battery: Important Tips


Disconnecting a car battery for any purpose will result in unexpected results. So there are a few things to consider before disconnecting a car battery.


To reset car computer after replacing battery safely, take note of the following:


  1. When the battery is removed, battery voltage must be maintained to the (PCM) and other modules. If the engine is running or the ignition key is switched on, never detach the car battery.


  1. When the car battery is disconnected, the electrical system will experience a high voltage spike. As a result, electronic modules are damaged. So, when your vehicle's memory starts to fail, things start to go wrong.


The loss of voltage to the powertrain control module (PCM) causes it to forget its adaptive memory settings on any vehicle with computerized engine controls. As a result, adaptive memory stores the changes that the (PCM) has learned over time — the fuel mixture, transmission change points, and other control functions, for example. All of the results from the diagnostic self-tests that the (PCM) performs on itself are stored in the keep alive memory.


With this disconnecting the car battery might cause these issues:


  • Problems when starting 
  • Issues in terms of vehicle’s drivability
  • Loss of air conditioning
  • Issues on power accessory functions ( seats, doors, windows, sunroof)
  • Inaccurate warning lights
  • Damage to electronic modules


On late model cars, disconnecting the car battery to reset the (PCM) will do more than just delete the keep alive memory. It can also delete crucial learned information that is needed for other modules to work properly. So it is best to know exactly what things can go wrong before you reset car computer after replacing battery as it is also dependent on the vehicle’s make, year and model.


The engine can run poorly if the car battery is disconnected. Since the air/fuel mixture is too rich or too lean, the fuel trim adjustments must be relearned before the (PCM) can. Until the (PCM) or transmission control module relearns the shift changes, the transmission also can not feel the same. The affected module can also interfere with the operation of the (ABS) or airbag systems.


Disconnecting the battery may also reset the climate control module. So, on some vehicles, that can mean the A/C will not be able to work until such time that  the module is programmed, with the correct set of instructions. 


The body control module (BCM) is also reset. This can cause power accessories to malfunction. Power windows, memory seats, a power sunroof, and electronic suspension settings are only a few examples. It can potentially reset or disable the vehicle’s anti-theft system. The engine will turn over, but it will not start since the anti-theft device believes that the car is being stolen.


Power window and/or power sunroof location settings can be lost if the battery is disconnected. The steering angle sensor settings have been lost. Following the battery disconnect, the steering angle sensor would need to be relearned.


On certain cars, replacing the car battery necessitates using a scan tool to enter the new battery information into the (PCM). Since the vehicle's charging mechanism is designed to progressively increase the charging rate as the battery ages, this is required. Finally, it causes an electronic radio and clock to lose their channel settings.


Reset Car Computer After Replacing Battery SAFELY


Secure a memory saver. A memory saver is nothing more than a connector with a small battery inside. While the car's main battery is disconnected, it has only enough voltage and current to hold all of the machine memory alive. In a nutshell, the connector connects to the cigarette lighter or the (OBD-II) connector in the vehicle.


On the positive side of the memory saver gadget, there is a diode. A diode is basically an electrical one-way valve. It prevents electricity from flowing backwards, which could cause harm. To use a memory saver, follow these simple steps:


  • Before disconnecting the battery, always switch off the engine. Then, using the cigarette lighter or the OBD-II connector, plug in the memory saver with its small battery. The OBD-II connector is mounted on the steering wheel, under the driver's side of the dashboard.


  • Remove the old battery next, making sure the positive battery wire does not come into contact with the car's body. After that, connect the connectors and mount the new battery.


  • Lastly, unplug the memory saver from the car at the end.


For the PCM/ECM to fully relearn LTFT values, it takes approximately 10 cold starts with a running period of 15-30 minutes. With each cold start during this period, the engine will run better and better.


Resetting ECM through the Fuse Box: Alternative to Reset Car Computer After Replacing Battery


Resetting your cars ECU, should not worry you so much as there are other alternatives to do it, such as resetting through the fuse box. Unplugging the battery or resetting the fuse related to the engine control module are the two most popular ways to reset your car computer.


It's also a good idea to reset the ECU when making adjustments to your engine. You'll need to manually reset your engine control modules via the fuse box in this scenario.The fuse box is next to the battery on the passenger side. Switch off your vehicle and unplug all fuses once it has completely warmed up, then detach the battery to cut power. 


All of the old data should be reset after a few minutes, so reconnect the fuses and restart your engine. Enable at least 10 minutes for your vehicle's ECM to “read” any new modifications you've installed.The auto ECU being a sensitive module has to be reset after making changes, otherwise the new modifications can interfere with the engine's previous operation.

Reset Car Computer After Replacing Battery: Related Questions

  • Which battery terminal do you disconnect to reset computer?


When removing the cables to reset the car computer, remove the negative first, and then positive. But if you only want to reset the car’s ECU, then removing only the negative is good enough. When installing cables, start with the positive and work your way to the negative.

  • Why would a car's computer need to be reprogrammed?


To remove every last ounce of horsepower, reprogramming would improve spark plug timing and fuel enrichment, as well as increase turbocharged engine pressure. You'll need to reprogramme your ECM to keep your vehicle control software up to date.

  • How do you tell if your car's computer is fried?


A poor or failing ECU will usually produce a few main symptoms that will alert the driver to a possible problem. Check Engine Light illumination, stalling or misfiring engine, engine output problems, and starting issues are some of the symptoms.

  • Can I drive with bad ECM?


If the ECM becomes damaged or defective, it will cause problems for the entire engine because it will not be properly controlled. If the engine is not properly controlled, it will not run properly, and the vehicle will not function properly.

  • Can you swap ECU from car to car?


You can absolutely use the same ECU in another car of the same make. But if the vehicle has an immobilizer, the vehicle will not start until the immobilizer is programmed to fit the VIN on the ECU.

  • Why does my radio not work after changing battery?


The most popular explanation for a car radio to stop functioning after the battery has died completely is that the radio has an anti-theft “feature” that activates once the battery is removed. If the radio has both power and field, it is most likely defective internally.

  • What is the code for a bad ECM?


The P0600 Code indicates that one of the sensors attached to your ECM is malfunctioning. Alternatively, it may simply be a wiring problem. The P0700 code indicates that there is a problem with your TCM (Transmission Control Module).


There are a number of situations when resetting your car’s computer is required but it is understandable that you can be a bit hesitant — either you do not know exactly how or you are simply worried about making a mistake during the process of disconnecting your battery. Hopefully this article answered a few of your questions so you can be a bit more confident the next time you reset car computer after replacing battery.

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