After changing battery does computer need to be.

  • 2006 MERCEDES BENZ E350
  • 70,000 MILES

After changing battery does computer need to be reset if so how

Thursday, January 10th, 2013 AT 4:20 AM

1 Reply

  • 29,070 POSTS

You did that by disconnecting the battery. The various computers lose their memory. What needs to be "reset" is the "look-up tables" the Engine Computer uses to determine how much fuel to command for any combination of operating conditions. It will start out with factory-programmed values, then begin to modify and adjust those numbers while you drive. Most of the time you won't even know that is taking place.

Most battery installers avoid the need for computers to relearn operating characteristics by using a "memory saver" device. Typically they use a nine volt transistor battery and plug into the cigarette lighter. You have to be careful with those to not open a door, turn on the under-hood light, or turn on the ignition switch. That tiny battery is too small to run lights and the fuel pump and will in effect be shorted out. I connect a small battery charger to avoid having to reset clocks and radios for customers, but that has its own precautions and dangers.

Some manufacturers have designed in some tricks to catch unsuspecting owners and cost them a lot of money. In particular, you can cause a lot of expensive misery when simply disconnecting the battery on Volkwagens, GMs, and BMWs. Memory saver devices become real important with cars like those.

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Friday, January 11th, 2013 AT 9:57 AM

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