Car lose some important memory settings when......

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Full title: Does your car lose some important memory settings when you replace the battery?

According to this: http://www.aa1car.com/library/battery_disconnect_problems.htm

Quote:
So what happens when the battery is disconnected? It depends on the year, make and model of the vehicle, but any of the following may happen:

It erases all the learned values in the PCM's Keep Alive adaptive memory. 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. This may take up to several days and 50 to 100 miles of driving until engine operation returns to "normal."
Erasing the PCM's adaptive memory may also affect the way the transmission shifts and feels. The transmission may not feel the same until the PCM or transmission control module relearns the shift adjustments. This may take 50 to 75 miles of driving.
It resets the FMEM (Failure Mode Effects Management) module on certain late model Ford vehicles. This module provides an adaptive fail-safe strategy that substitutes estimated or fixed data for missing sensor data. Normally, this should not cause a problem UNLESS the vehicle has a bad sensor and has been substituting data from the FMEM module for a missing input.
It resets the ABS (Antilock Brake System) and SIR (Supplemental Inflation Restraint) or airbag modules. This should not be a problem UNLESS one of these modules requires a special relearn or reprogramming procedure after power has been lost. In that case, the affected module may prevent the ABS or airbag systems from working.
It resets the Climate Control module. On some vehicles, the module will not start working again until a special relearn procedure or reprogram procedure is performed with a factory scan tool. That means no A/C until the module is programmed with the correct instructions.
It resets the Body Control Module (BCM). Like the Climate Control module, the BCM may not resume normal operation until it has undergone a special relearn procedure or is reprogrammed with a factory scan tool. This can mess up the operation of power accessories such as power windows, memory seats, power sunroof, or electronic suspension settings. Worse yet, the BCM is the "gate keeper" module on many 2003 and newer vehicles that have a CAN (Controller Area Network) system. If the BCM cannot communicate properly with all of the other modules, or it does not recognize the addresses of other modules, it can cause all kinds of problems.
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. Again, it may require a special relearn procedure or reprogramming the anti-theft system with a factory scan tool to resolve the problem.
It causes a loss of channel settings on an electronic radio and clock. This is more of an annoyance than a problem, and can be fixed by resetting the radio channels and the time.


it would seem worthwhile to find a way to preserve the ECM settings.

In my case, after replacing the battery, the car began to idle rough (around 400rpm) but the problem went away after some driving, but the fuel economy is still worse. I guess the computer has to re-learn a few things. I am hardly the only person to have had this problem after replacing the battery.



So, question: Does your car have to re-learn a few things when swapping out batteries? If so, what DID you do to mitigate this problem?
 
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Depending upon how the power adapter wiring is set up, you can sometimes keep everything backed up by a 9v battery.
 
I ended up making a "memory saver" out of batteries and an accessory plug to save time whenever I disconnected tha battery.

Saves lots of time restting customer radio stations/idle strategy/climate control settings.
 
Radio lock codes are a pretty nice moneymaker for dealers.

Who, seriously, steals a stock radio?

Who is so vain that with their day old new car they read the owners manual and set a stupid code that they and everyone else promptly forgets?
 
Both the expedition and the mustang lost the PCM programming when the battery was disconnected. The transmission shift hard for a week or two after, until it relearns.
 
I've seen an external battery that plugs into the accessory/cig lighter to prevent losing everything-seems to cause more trouble on newer vehicles. I let my Dodge sit too long & the batteries got weak-actually threw a code & I had to borrow a code reader to reset it!
 
If your car is in good running condition: i.e. EGR valve working, O2 sensors fine, IAC valve is functional (not binding/stuck or carboned up, etc.), chances are, unplugging your battery and then re-connect to intentionally/unintentionally reset computer memory isn't gonna make things any worse.

You have to remember this: with both OBD-1 systems, ECU already stored a predefined set of criteria (settings, voltage reading range, etc.) for all the sensors involved.

With OBD-2: in addition to the predefined set of criteria already stored inside the ECU, it has the additional capability to "learn" and adapt to the change imposed onto the sensors it is configured to "read". Things like transmission shift points, gas pedal (acceleration) in relation to the driving speed/transmission shifting behaviour, etc. Re-setting the computer on these OBD-2 system is just gonna roll back to it's default state, which is equivalent to the day that the vehicle rolled out of the factory assembly plant (default settings).

Also: OBD-2 systems are designed to "learn" and "adapt" fairly quickly, typically within 10~30miles of regular form of driving.

So, bottomline is, why fuzz over the memorized settings of an ECU? (I sure wouldn't, for I've been dealing with OBD-1 and 2 for 2 decades and I never experience any driveability-related issues with ECU rolled back to default after a power reset).

Quest
 
A good way is to connect a common 9V battery with leads to the terminals, if you change a battery. [short term]
A battery charger can also be connected.
This will keep the clock and radio OK, too.
But disconnecting and relearning can also CURE problems.
A fresh start is sometimes a great idea.
 
You took too long to replace it. If you replace it quickly enough this won't happen. You lost your keep alive memory (KAM) which are the settings your ECU uses based on your particular vehicle to optimize performance (including gas mileage and smoothness). The ECU has to relearn these things after the KAM has been wiped, but it does relearn it. That is why your rough idle went away and your MPG are down. Fear not though, they will come back.

They sell memory savers that plug into the cigarette lighter which will prevent this. It is a good practice to use one. However, on the newer Toyotas, there is a diode inline with the cigarette lighter which prevents backflow from the cigarette lighter to the electrical system. In this case, a memory saver must be connected to the battery terminals of the vehicle in order to save the memory while you work.

Hope this helps,
Techniker
 
Originally Posted By: OneEyeJack
Would it hurt anything to hook up a battery charger to the terminals and then change the battery?


Of course you can hook up a properly functioning battery charger. Won't hurt a thing in the computer. And like I mentioned, you can use a charger to keep your memory alive while changing out the battery.
 
$4.39 at your local Advanced Auto

9020059_atc_ac590_pri_larg.jpg
 
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