If I Reset BCM......what to expect



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Thread: If I Reset BCM......what to expect

  1. #1
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    If I Reset BCM......what to expect

    So I have read several BCM issue threads, most seem to recommend disconnecting the battery for a couple of days to reset the BCM.

    If I do disconnect the battery for a couple of days to reset the BCM......what should I expect when I reconnect it ? Just what will be missing ?

    BTW, my issue is my locks are going nuts.....see previous post.
    At present: 01 T&C Ltd. AWD 3.8
    Other cars:
    99 Corvette 08 Miata MX5

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    To answer your PM, here's a couple places you can get a new/rebuilt BCM or have yours rebuilt. Fish through this forum and automotiveforums.com and you'll find more. Type variations in the search function and you should see somethiung pop up.
    http://bbb-carb.com/chrycomputer.htm
    http://www.goecm.com/

    What will you loose when disconnecting the battery? Your radio presets if that matters. Most importantly you'll loose the shift sequencing/scheduling parameters saved in the Transmission Control Module (TCM). What is that crap? As you drive, the TCM "learns" or saves information about how you drive the van in order to provide smooth and efficient shifting as you go through the gears. When you disconnect the battery, all that information is lost. Whenever a shop disconnects the battery they are supposed to do what is called a "quick learn" procedure using a scanner to give the TCM basic parameters. The reality is, many don't AND you never know it. BUT BUT YOU JUST SAID...

    More reality. Yes, the manual says to perform a quick learn. Based on what I've read on several forums over the last 5 years and experience with my van and three others, in my opinion it's not absolutely necessary. Few have any issues without the quick learn. I've disconnected batteries many times without doing the quick learn and haven't noticed any problems. Some have reported harder shifting for a few days until the TCM "relearns" on it's own. I've have read of serious problems that could be attributed to not doing a quick learn procedure but only once or twice in all the years I've been reading forums and DIYn. Bump that against all the battery disconnects that happen across the country. Your chances of having a problem without doing a quick learn are nill. That's not to say you shouldn't take advantage of a simple option to avoid the possibility of transmission damage. That's why in your situation with the BCM I recommend pulling the IOD fuse to reset the BCM instead of disconnecting the battery. That avoids any chance whatsoever of having a subsequent transmission problem.

    You can perform a quick learn manually. If it's a concern, let me know.
    Last edited by RIP; 01-26-2009 at 03:42 PM.
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  4. #3
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    Quote Originally Posted by RIP View Post
    To answer your PM, here's a couple places you can get a new/rebuilt BCM or have yours rebuilt. Fish through this forum and automotiveforums.com and you'll find more. Type variations in the search function and you should see somethiung pop up.
    http://bbb-carb.com/chrycomputer.htm
    http://www.goecm.com/

    What will you loose when disconnecting the battery? Your radio presets if that matters. Most importantly you'll loose the shift sequencing/scheduling parameters saved in the Transmission Control Module (TCM). What is that crap? As you drive, the TCM "learns" or saves information about how you drive the van in order to provide smooth and efficient shifting as you go through the gears. When you disconnect the battery, all that information is lost. Whenever a shop disconnects the battery they are supposed to do what is called a "quick learn" procedure using a scanner to give the TCM basic parameters. The reality is, many don't AND you never know it. BUT BUT YOU JUST SAID...

    More reality. Yes, the manual says to perform a quick learn. Based on what I've read on several forums over the last 5 years and experience with my van and three others, in my opinion it's not absolutely necessary. Few have any issues without the quick learn. I've disconnected batteries many times without doing the quick learn and haven't noticed any problems. Some have reported harder shifting for a few days until the TCM "relearns" on it's own. I've have read of serious problems that could be attributed to not doing a quick learn procedure but only once or twice in all the years I've been reading forums and DIYn. Bump that against all the battery disconnects that happen across the country. Your chances of having a problem without doing a quick learn are nill. That's not to say you shouldn't take advantage of a simple option to avoid the possibility of transmission damage. That's why in your situation with the BCM I recommend pulling the IOD fuse to reset the BCM instead of disconnecting the battery. That avoids any chance whatsoever of having a subsequent transmission problem.

    You can perform a quick learn manually. If it's a concern, let me know.
    Thanks very much,

    Actually I did quite a few searches on rebuilt BCMs and got back nothing......then I saw your post.
    I did change out my battery just last week and there was no battery for about 15 minutes......but I didn't notice any changes beyond losing the radio settings. Some have said the battery needs to be disconnected for several hours ??

    This is my second 3rd Gen but #1 was a brand new 96 and besides two transmissions replaced under warranty it was problem free. This 99 has had at least three owners before me and has it's share of issues......so I am trying to resolve as many as I find in a timley manner.

    Thanks again,

    Jim
    At present: 01 T&C Ltd. AWD 3.8
    Other cars:
    99 Corvette 08 Miata MX5

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    Quote Originally Posted by jrprich View Post
    Thanks very much,

    Actually I did quite a few searches on rebuilt BCMs and got back nothing......then I saw your post.
    I did change out my battery just last week and there was no battery for about 15 minutes......but I didn't notice any changes beyond losing the radio settings. Some have said the battery needs to be disconnected for several hours ??

    This is my second 3rd Gen but #1 was a brand new 96 and besides two transmissions replaced under warranty it was problem free. This 99 has had at least three owners before me and has it's share of issues......so I am trying to resolve as many as I find in a timley manner.

    Thanks again,

    Jim
    Some say to touch the positive terminal to the negative terminal, once removed from the battery.
    I guess that would be to quickly discharge any capacitors. I don't think you would have to leave the battery disconnected for hours for that to happen though.
    RIP's the man for this stuff.
    2007 GC SXT - Magnesium - S&G - 3.8L - 115,600 kms
    2002 GC Sport - Stone White - 3.3L - 314,240 kms
    2003 Jeep TJ Sport - 4.0L - 246,430 kms

  6. #5
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    Well I just pulled the IOD fuse for 30 sec......and I am amazed that the locks seem to work now

    Took me awhile to find the IOD fuse as I thought it would be a 20 amp......but only 10 amp on the 99 and hidden way up in a corner.

    Hope this works, I will visit the dealer tomorrow and try again to get a FOB programmed.

    THANKS TO ALL
    At present: 01 T&C Ltd. AWD 3.8
    Other cars:
    99 Corvette 08 Miata MX5

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    Hopefully all is well with the door mechanism / BCM.

    IOD (Ignition Off Draw) fuse .... mmmmm .... remove this 10 amp fuse for 20 seconds and the BCM resets itself and lot of little annoyances go away. Sounds like a handy thing to know. Here's a list from this site of functions controlled by the BCM:

    http://wiki.answers.com/Q/What_is_a_BCM_fuse

    The BCM provides the following features:

    Automatic door locks
    Battery protection
    Chimes
    Compass/mini-trip support
    Courtesy lamps
    BCM diagnostic support
    Door lock inhibit
    Headlamp time delay
    Ignition key lamp
    Illuminated entry
    Instrument panel dimming
    Mechanical instrument cluster support
    Power door locks (with/without remote keyless entry)
    Sliding door memory lock
    Vehicle Theft Security system (VTSS)
    Windshield wipers / washers (front and rear)
    2007 GC SXT - Magnesium - S&G - 3.8L - 115,600 kms
    2002 GC Sport - Stone White - 3.3L - 314,240 kms
    2003 Jeep TJ Sport - 4.0L - 246,430 kms

  8. #7
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    Hmmmmmmm

    May have spoken too soon.

    When I went back out to the van a few minutes ago, my locks again did their crazy dance

    Also I still can't get the auto locking to reset and work......no chimes after running through the steps.

    Guess i will see what the morning brings when I get ready to try the dealer again for a fob program.

    These locks are nuts
    At present: 01 T&C Ltd. AWD 3.8
    Other cars:
    99 Corvette 08 Miata MX5

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    Quote Originally Posted by jrprich View Post
    Hmmmmmmm

    May have spoken too soon.

    When I went back out to the van a few minutes ago, my locks again did their crazy dance

    Also I still can't get the auto locking to reset and work......no chimes after running through the steps.

    Guess i will see what the morning brings when I get ready to try the dealer again for a fob program.

    These locks are nuts
    Seems like a connection issue (loose, corrosion or poor ground). That's just a gut feeling?
    Common location for intermittent connection issues is the "bending" wires in the door hinge area.
    2007 GC SXT - Magnesium - S&G - 3.8L - 115,600 kms
    2002 GC Sport - Stone White - 3.3L - 314,240 kms
    2003 Jeep TJ Sport - 4.0L - 246,430 kms

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    Quote Originally Posted by Jeepman View Post
    Seems like a connection issue (loose, corrosion or poor ground). That's just a gut feeling?
    Possibly.....but there are thousands of connections.......where to start
    At present: 01 T&C Ltd. AWD 3.8
    Other cars:
    99 Corvette 08 Miata MX5

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    Does anyone know if resetting the BCM will clear the memory seat/mirror settings? My memory settings have NEVER worked. I made the mistake of programming my FOB to recall memory 1 and the mirrors and seat always move to the wrong position, no matter how many times I set the positions and set the memory again, so everytime I get in I have to readjust the mirrors and the seat positions. It just doesnt work. ('97 T&C LXi) Any ideas? I've tried unplugging the battery for 30mins to and hour. Nothing. What about pulling the IOD fuse?
    Last edited by sideburns2009; 01-29-2009 at 04:07 PM.
    2001 Infiniti i30 3.0 DOHC V6: VQ30DE 177,000 miles; 1999 Nissan Altima GLE KA24 168,000 Miles
    1997 Dodge Ram 1500 SLT Laramie 5.9 46RE, 182,000 Miles
    Prev. 97 T&C LXi 184k 3.8, 94 T&C 3.8 156k Miles, 93 GV LE 3.3 123k

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