Dead battery, need to reset the computer ??
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    1. #1
      Member Mr. P's Avatar
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      Jun 2004
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      Tennessee
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      Dead battery, need to reset the computer ??

      Due to longtime inactivity my battery on the 2005 XC70 finally totally discharged. Now my odometer does not work (and several other things)

      Is there some way to do a reset for the computer ??

      The brake and ABS warning are also on but the car drives just fine like it did before the long slow loss of battery power.
      2005 XC70 2.5 AWD, 2008 XC90 3.2 AWD, 1983 928S 5-speed, 1984 944, 1990 S2 Cabriolet, 1974 TVR 2500-M..

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    3. #2
      Junior Member
      Join Date
      Sep 2018
      Posts
      261
      Try doing a "cold reboot" of the computer module network (req'd for P2 Volvos):
      1) With battery fully charged up, disconnect the negative battery terminal -- wait 5 min for all capacitors to drain.
      2) Move ignition key to "II" position
      3) Reconnect battery terminal in one smooth action (no bounce). Wait 2 minutes for all modules to startup.
      4) Start engine -- evaluate all dashboard displays and functions

      If you're still seeing issues, have the battery checked.

      A weak battery will not be able to hold system voltage above 12.3 Vdc while starter motor is drawing cold-cranking amps. Result: some computer modules go into low-voltage resets and get out of sync during starter cranking.

      If you have a sampling voltmeter, you can measure the minimum battery voltage during cold engine start.

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