So, Most people do not realize that disconnecting a car battery for any reason; may cause unexpected things to happen.
As a result, Before you disconnect a car battery; there are things you need to know.
Battery voltage MUST be maintained to the (PCM); and other modules while the battery is being disconnected.
Regardless of; the year, make or model of vehicle; NEVER disconnect the car battery while the engine is running or the ignition key is turned on.
Disconnecting the car battery can create; a high voltage spike in the electrical system; that may damage electronic modules.
So, Loss Of Memory Is Where Things Start To Go Wrong
On any vehicle that has computerized engine controls; the loss of voltage to the powertrain control module (PCM); causes it to forget its adaptive memory settings. Consequently, Adaptive memory contains the adjustments the (PCM) has learned over a period of time; for the fuel mixture, transmission shift points and other control functions. The keep alive memory also includes; all the results for the diagnostic self-tests the (PCM) runs on itself.
As a result, Disconnecting A Car Battery; On Computer Equipped Vehicles; May Cause A Whole List Of Issues;
- Starting problems
- Driveability issues
- Loss of air conditioning
- Power accessory functions (door windows, seats, sunroof)
- False warning lights
- Damage to electronic modules
So, Disconnecting the car battery to reset the (PCM) on late model vehicles; can do more than just erase the keep alive memory. It can also erase vital learned information; that is absolutely necessary; for other modules to function normally.
Learn What Can Go Wrong; Before You Disconnect Your Car Battery
What Will Happen When The Battery Is Disconnected Depends On; The Year, Make And Model Of Your Vehicle;
- This may cause the engine to run poorly; because the air/fuel mixture is too rich or too lean for a period of time; until the (PCM) can relearn the fuel trim adjustments.
- The transmission may not feel the same; until the (PCM) or transmission control module relearns the shift adjustments.
- The affected module; may prevent the (ABS) or airbag systems from working.
- It also; resets the climate control module. On some vehicles; That means the A/C will not work until the module is programmed with the correct instructions.
- It also; resets the body control module (BCM). This can mess up the operation of power accessories such as; power windows; memory seats; power sunroof; or electronic suspension settings.
- It may; reset or disable the anti-theft system. The engine may crank but not start; because the anti-theft system thinks somebody is trying to steal the vehicle.
- Loss of power window and/or power sunroof position settings.
- Loss of steering angle sensor settings. The steering angle sensor will have to undergo a relearn procedure; following the battery disconnect.
- Replacing the car battery on some vehicles; requires entering the new battery info into the (PCM) with a scan tool (type, serial number and CCA rating). This is necessary; because the vehicle’s charging system is; programmed to gradually increase the charging rate as the battery ages.
- It causes a loss of channel settings on an electronic radio and clock.
Learn How To Safely Disconnect Your Car Battery
A Handy Tool Everyone Could Use Is A Memory Saver.
A memory saver is simply; a connector with a small battery; that has just enough voltage and current; to keep all of the computer memory alive; while the cars main battery is disconnected. The connector plugs into the car’s cigarette lighter; or the (OBD-II) connector.
The memory saver tool incorporates a diode on the positive side. A diode is essentially; a one-way valve for electricity. It will stop the electricity from; flowing backwards; causing damage.
The steps to use a memory saver are easy;
- Before the main battery is disconnected; make sure the car is turned off.
- Then, plug in the memory saver; with its small battery attached into the cigarette lighter or the OBDII connector.
- The OBDII connector is located under the driver’s side of the dashboard; on the steering column.
- Next, remove the old battery; making sure that the positive battery wire is not touching the car’s body.
- Then, install the new battery and attach the connectors.
- Finally, unplug the memory saver from the car. That’s all.
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