Will a disconnected battery reset the ECU

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Do modern cars have some kind of power reserve for the ECU memory or does the ECU reset itself when the car battery is removed ?

I need to remove the battery from my Logan DLS for charging (a bad light switch in the boot caused the light to stay on for 5 days and discharged the battery) and was wondering if its ok to leave the ECU powerless for about 15 hrs.

Luckily I have a battery charger at home smiley1.gif

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The ECU does not get Reset even if the Battery is removed. To Reset the ECU, you have to program it using special tools.

   The only things which get reset after removing the Battery are the Digital Clock (if fitted on the Dashboard), the settings of Car Audio System (The clock and other settings present in Audio are reset to their Factory Default Settings). You can leave the ECU powerless even for 1 month.

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Some values may be reset. But they won't cause any problems because the default programming will remain. So don't worry and charge that battery.


Thanks FRG - thats what I was looking for - Sorry if some people were confused by ECU reset vs. a reflash/remap.

I understand that the ECU is going to start "learning" all over - but was confused as some people recommend idling the engine after doing such a thing while others recommend that the car be driven hard smiley5.gif

It would be great if you could help me understand what values are stored outside the ROM (the ones that would be lost)

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