Hot!Effects of disconnecting the battery

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Richard_Hamilton
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Richard_Hamilton PCGB Member
2013/06/01 13:52:12 (permalink)

Effects of disconnecting the battery

Extracted from the workshop manual, I thought this might be useful:


Effect of disconnection or total discharge of battery on electrical systems in the vehicle and the precautions to be taken. (MY2005-on)

Control unit memories
Values and faults stored in the control units can be deleted if the battery is disconnected or completely discharged.
  • If possible, all fault memories should be checked and, if necessary, printed out before the battery is disconnected.

    Supply voltage fault entry
    The entry "supply voltage" may be stored in various control units if the battery has been completely discharged.
  • Delete the "supply voltage" entry from the control units in question.

    Ready status
    In some countries (presently the U.S.A. and Canada), after disconnecting the battery, it is necessary to reach the Ready status by a test drive and/or by using the Porsche System Tester DME control module menu). If in doubt about this, contact the relevant importer.

    DME control module
    With all DME systems, the engine must run for several minutes before the engine control module can relearn the idle speed and mixture adaptation values!
    After disconnection of the power supply, the idle speed might change or fluctuate briefly until the throttle valve adjusting unit has been readapted.
    The mixture adaptation is also lost.

    After the battery is connected:
    With the DME, it is necessary to carry out a learning and adaptation routine as described below:
  • Switch ignition on for 30 seconds without starting the engine.
  • Do not actuate accelerator pedal.
    This completes the adaptation of the throttle valve adjusting unit.

    Tyre pressure monitoring system
    When the battery is disconnected and connected, the tyre pressure is first displayed as "- - - ".
  • Once the battery has been disconnected and work is complete, the vehicle must be driven for a short distance.
    The actual pressures will then be displayed again.

    Steering angle sensor (PSM)
    The steering angle sensor must be re-initialised when the battery is disconnected and connected.
  • Turn wheels to straight-ahead position.
  • Switch ignition off and then on again twice.
  • Start engine.
  • From the straight-ahead position, turn steering wheel approx. 20° to the right, past the straight-ahead position.
  • Drive the vehicle straight ahead for at least one second at a speed above 4 km/h (2.5 mph).
    The steering angle sensor segment is recognised again in this process.
    Once the sensor has been successfully initialised, the fault code that is stored in the fault memory is documented using the fault deletion counter.
    The fault memory erases itself automatically.
    The PSM indicator light in the instrument cluster goes out.

    Power windows
    The end positions of the power windows are deleted from the control unit when the battery is disconnected and connected.
    Perform the following procedure for all power windows:
  • Actuate rocker switch and fully close window once.
  • Actuate rocker switch once more to close.
    The upper end position of the window is stored.
  • Actuate rocker switch and fully open window once.
  • Actuate rocker switch once more to open.
    The lower end position of the window is stored.

    Instrument cluster
    Clock
    The time is deleted when the power supply is disconnected.
  • Press clock control button approx. 1 second on instrument cluster. Hour display flashes.
  • Press clock control button in the corresponding direction. Hours can be adjusted.
  • Press the clock control button again, the minute display flashes and can be adjusted by turning the clock control button.
    Trip odometer
  • The trip counter is set to 0 when the power supply is disconnected.

    Airbag control module
    If the battery is disconnected for less than 100 seconds when the ignition is switched on, a CAN time fault, which makes diagnosis of the airbag control unit impossible, may be stored in the airbag control unit.
  • The fault is erased by removing the ignition key.

    On-board computer
    Disconnection of the vehicle battery deletes the memories for average speed and average consumption. As a result, the displayed range on remaining fuel can be markedly different or even 0. The outside temperature display loses its memory effect. In other words, the indicated outside temperature can be too high due to the heat radiated when the vehicle is hot.

    PCM
    When the power supply is disconnected, the built-in GPS receiver loses the so-called almanac containing the satellite orbital paths.
  • Switch on PCM when there is a free panoramic view (load GPS almanac); the almanac is reloaded as soon as four satellites have been identifed.
    The date and time are deleted when the battery is disconnected. The summer-/wintertime recognition feature is maintained. The time is lost and is updated again when there is a plausible GPS reception (four satellites).
  • The date and time are also adopted once the GPS almanac has been loaded; it may be necessary to change over to summer time (daylight-saving time). This time is transferred to the instrument cluster. If the time is then manually changed by means of the instrument cluster, this time is adopted by the PCM and synchronised with GPS time.
    If the telephone card had been inserted and the telephone was ready for operation, the telephone is subsequently disabled (only if "Use last PIN" is deactivated).
  • The telephone is enabled again when the telephone PIN code is entered with the SIM telephone card inserted.

    Test drive after disconnecting battery
    Depending on the vehicle equipment fitted, all these work steps are carried out during the test drive.
    Read out the fault memories of all control units after the test drive.
  • If there is a fault present, check to see if the fault was caused by an undervoltage.
  • If faults were caused by an undervoltage (or CAN timeout error), erase the fault memory, perform another test drive and read out the fault memory.
  • If faults were not caused by an undervoltage, correct the faults in accordance with GFF (Guided Fault Finding).



  • Richard
    1989 3.2 Carrera Sport in Guards Red/Linen & Audi RSQ3
    Previous:
    2012 Cayman 2.9 PDK, 2006 Cayman S, 2000 996 Turbo, 1998 996 C2, 1994 993 C2

    51 Replies Related Threads

      Giff
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      Giff PCGB Member
      RE: Effects of disconnecting the battery 2013/06/01 15:01:35 (permalink)
      How long is it necessary to have the battery disconnected before needing to go through this process?
      Or is all memory lost straight after disconnection?
      Richard_Hamilton
      PCGB Member
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      Richard_Hamilton PCGB Member
      RE: Effects of disconnecting the battery 2013/06/01 15:10:52 (permalink)
      Pretty much instant with most modules, I believe.

      Richard
      1989 3.2 Carrera Sport in Guards Red/Linen & Audi RSQ3
      Previous:
      2012 Cayman 2.9 PDK, 2006 Cayman S, 2000 996 Turbo, 1998 996 C2, 1994 993 C2
      BrianJ
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      BrianJ PCGB Member
      RE: Effects of disconnecting the battery 2013/06/01 15:55:13 (permalink)
      Handy stuff Richard, many thanks.

      Brian J
      Was 2003 986 2.7 facelift (80k in that).
      Was 2009 Gen II Cayman S (47k in that).
      Now 2013 981 Boxster S (25k so far)
      Derbyshire Peak District
      M666LMJ
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      M666LMJ PCGB Member
      RE: Effects of disconnecting the battery 2013/06/01 16:31:29 (permalink)
      Hi Richard.

      I know this is the wrong forum. But are the effects of battery disconnection the same for a 996?

      Mike

      2014 991.1 Carrera GTS Lime Gold
      2015 Mini Cooper S Volcanic Orange
      2007 BMW E91 318d SE Touring Black Sapphire
      Previous forever Porsches:
      2012 991.1 C2S Cab Basalt Black
      2007 997.1 Turbo Meteor Grey
      2002 996.2 C4S Midnight Blue

      Richard_Hamilton
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      Richard_Hamilton PCGB Member
      RE: Effects of disconnecting the battery 2013/06/01 21:09:05 (permalink)

      ORIGINAL: M666LMJ

      Hi Richard.

      I know this is the wrong forum. But are the effects of battery disconnection the same for a 996?

      Mike

      Most systems are different on the 996. For example, the PSM isn't affected by a battery disconnection, but it usually gives a heart stopper message on a 9x7. Window resetting and DME adaption are different. I'll try to post something on the 996 forum in a day or two.

      Richard
      1989 3.2 Carrera Sport in Guards Red/Linen & Audi RSQ3
      Previous:
      2012 Cayman 2.9 PDK, 2006 Cayman S, 2000 996 Turbo, 1998 996 C2, 1994 993 C2
      M666LMJ
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      M666LMJ PCGB Member
      RE: Effects of disconnecting the battery 2013/06/01 21:14:22 (permalink)
      Hi Richard.

      Look forward to it. Always a pleasure

      Mike

      2014 991.1 Carrera GTS Lime Gold
      2015 Mini Cooper S Volcanic Orange
      2007 BMW E91 318d SE Touring Black Sapphire
      Previous forever Porsches:
      2012 991.1 C2S Cab Basalt Black
      2007 997.1 Turbo Meteor Grey
      2002 996.2 C4S Midnight Blue

      Guest
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      Guest Guest of the Club
      RE: Effects of disconnecting the battery 2013/11/26 14:05:23 (permalink)

      Control unit memories
      Values and faults stored in the control units can be deleted if the battery is disconnected or completely discharged.


      Does this indicate that faults can either be deleted or avoided if you disconect the battery?
      Guest
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      Re: RE: Effects of disconnecting the battery 2015/10/17 15:28:56 (permalink)
      Our 2004 porche cayenne battery was dead, I left the lights on over night.  We trickle charged the battery.  It shows full, but when you put key in, dash lights up but engine will not turn over.  No messages on dash,  any ideas?
       
       
      Guest
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      Re: RE: Effects of disconnecting the battery 2015/10/22 21:02:59 (permalink)
      You need a normal charger.
      Guest
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      Re: Effects of disconnecting the battery 2015/11/12 20:02:21 (permalink)
      Hi Richard regarding disconnecting Battery does all this apply to the Boxster 981 many thanks Frank
      R1cardo
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      R1cardo Guest of the Club
      Re: Effects of disconnecting the battery 2015/12/04 19:44:05 (permalink)
      Do you happen to know if this proceedure works on a 2008 911 3.6 ?
      Thanks
      Richard
      Guest
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      Re: Effects of disconnecting the battery 2016/05/27 22:49:10 (permalink)
      I have a 2007 Cayman s. The battery went dead so charged it and now the dash lights won't come on and the key sticks in the ignition. Any ideas on how to solve this?
      Motorhead
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      Motorhead PCGB Member
      Re: Effects of disconnecting the battery 2016/05/28 09:10:09 (permalink)
      Something to try.
       
      Since its a potential security issue leaving the key in the ignition, in the fuse box you will find a thin metal hook. On the ignition barrel and beside the slot you will find a small door. Flip this open and insert the rod to release the key.
       
      You should find some reference to this in your Driver's Manual - it's on p57 for my gen2 Cayman.
       
      Jeff

      987.2 Cayman S
      North Bedfordshire
      PCGB R10 and R24
      Guest
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      Re: Effects of disconnecting the battery 2016/06/22 20:52:51 (permalink)
      Hello folks I'm new in the forum and I have read your posts but haven't found the answer, maybe you can help me. I recently own a 2001 Porsche 996 turbo tiptronic and the instrument cluster indicates a failure: "ONBOARD COMPUTER ERROR". The display in the instrument cluster doesn't indicate temperature, range of the car or turbo boost pressure and all those kind of average measures.
      My mechanic tells me that I should change all the instrument cluster but I don't think there is the problem since all other things such as low gas level alert, no fastened seat belt and others are OK.  Have anyone had this same situation may when havong replacing the battery or know what would I have to repair or change ?
      A permanent signal of "ON BOARD COMPUTER ERROR" makes me crazy.
       
      Thanks
       
      EDUARDO ROZO
      erozoferrero@yahoo.com.co
      Guest
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      Re: Effects of disconnecting the battery 2016/07/16 14:10:58 (permalink)
      HOW DO I GET THE AIR BAG LIGHT OFF AFTER BATTERY CHANGE?????  PLEASE HELP
      Motorhead
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      Re: Effects of disconnecting the battery 2016/07/16 18:02:53 (permalink)
      I think you'll need either to go to a Porsche Centre or to an Indie with the appropriate diagnostic capability to get the warning light extinguished.
       
      Jeff

      987.2 Cayman S
      North Bedfordshire
      PCGB R10 and R24
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      Re: Effects of disconnecting the battery 2016/07/30 18:31:18 (permalink)
      Dear all,
      Recently i charged my battery. 
      Now, when i start the car i can hear a "high voltage" sound for a second, only when i turn the key to start the engine. When i turn off the car and wait for 2 minutes snd try to turn the car on no sound. But if i turn the car off and turn it on with out waiting the i can hear that "voltage" sound.  
      Buddy
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      Buddy PCGB Member
      Re: Effects of disconnecting the battery 2016/08/01 08:36:30 (permalink)
      Different problem for me yesterday, climbed in turned the key click click click .... lights flashing and no start.checked the earth on the battery and the fuses all in place as apparently some cars have had these problems as reported by Ralphmusic still no go, trickle charged the battery to fully charged and it didn't take long to boost up still nothing calling the OPC later this morning when I have time... being retired is so busy!

      Kevan
      Cayman Register Secretary
      Cayman S Gen2 PDK Amethyst Metallic
      Location South Derbyshire
      PCGB R8
      Buddy
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      Re: Effects of disconnecting the battery 2016/08/02 11:34:34 (permalink)
      Battery checked and one cell dead, down to 10Volts Alternator output checked and found ok but battery not taking much charge, new battery bought and charged, swapped and Richards list gone through to ensure everything set, no problems, connected OBD2 to check for codes all ok.
       
      As a precaution I left the old battery connected so that at least memories were without power for the minimum of time.

      Kevan
      Cayman Register Secretary
      Cayman S Gen2 PDK Amethyst Metallic
      Location South Derbyshire
      PCGB R8
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