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Thread: Trans Fail Safe Prog+

  1. #1
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i

    Trans Fail Safe Prog+

    I've narrowed down when the car will go into limp mode. Now I need help in guidance as to what is causing it.

    When I drive with the transmission selector on AUTOMATIC the car will drive great in 1st gear and when it's time for the transmission to shift into 2nd gear the car won't shift and throws the Trans Fail Safe Prog+ message on the MID. At this point pressing the ASC button will not show "on" at gauge cluster and neither "E", "M" or "S" is displayed at the transmission mode display (located just left of mileage display). The car runs great and no misfiring just no power even if I floor the gas. The car just increases speed nicely but without torque. Moving the shifter through the gears on my driveway I notice the shift into and out of reverse is is abrupt/clunky.

    I can then get home, turn off the car, remove the key from the ignition, let it sit for a moment and restart the car. At this point the Trans Fail Safe message is no longer displayed on the MID, the ASC button works and so does switching from Automatic to Manual changes the display back and forth between E & M on the display and the shifting into and out of Reverse is smooth as butter.

    Now I can put the transmission on MANUAL shift mode and drive around manually shifting and this will NOT cause the Trans Fail Safe message.

    So, is there a transmission shift sensor, module, relay, fuse, etc. that I can check, repair, replace? TIA!
    Last edited by The Pondman; 02-14-2021 at 02:39 AM.

  2. #2
    Join Date
    Sep 2008
    Location
    Santa Barbara
    Posts
    3,462
    My Cars
    91 Dinan860 & 91 850 6sp
    selector switch under the shifter
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  3. #3
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    some pics from E32 selector switch, damaged https://www.bimmerforums.com/forum/s...ssion+selector
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i
    Thank you! I'll check that today.

    - - - Updated - - -

    Quote Originally Posted by cartoonz View Post
    selector switch under the shifter
    Thank you! I'll check that today.

    - - - Updated - - -

    Quote Originally Posted by shogun View Post
    some pics from E32 selector switch, damaged https://www.bimmerforums.com/forum/s...ssion+selector
    Awesome! I, like many others, truly appreciate the time taken to create all those write-ups with step-by-step instructions and photos. Thank you!

  5. #5
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i
    Is this bad enough to cause the problems mentioned? Also, is this loose pin just sits in that position? There are similar holes on the other side of the shifter but there's no pin in those holes.

    The A/M switch looks a little crusty so I'll try to clean it as well.

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    20210214_130205.jpg
    20210214_130212.jpg
    20210214_130724.jpg

  6. #6
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i
    Found a new gear selector switch so ordered one just to make sure.

    Though the outside of the A/M switch looks crusty, the inside was clean. I'll spray contact cleaner and put it back together as this is as far as I'm taking it apart. The bulb looks a little sketchy but does work.

    Anyone know the part# to the A/M switch? All the ones I find online look the same but are for other models and the pins are either in different configurations or have different plug types. TIA

    20210214_140516.jpg
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    Last edited by The Pondman; 02-14-2021 at 02:20 PM.

  7. #7
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i
    All clean, now let's see if this fixes my problem......
    20210214_160340.jpg

  8. #8
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i
    A big THANK YOU to both cartoonz & shogun! I cleaned the A/M mode switch and the gear selector switch and the car shifts properly in both automatic and manual mode without theTrans Fail Safe message. Thanks again!

  9. #9
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    good to hear, there is also a write up with pics on my website to clean the switch, http://twrite.org/shogunnew/topmenu.html on the index to the left see other BMW models, there click E34 transmission.
    Use mild sanding paper to clean the tracks of the code plate. The wiper should be readjusted by way of gentle pushing away from its frame the connectors to insure good engagement with code plate tracks.
    Gently push the screw driver perpendicularly to the connectors towards the base of their mounting. The deformation should be substantial enough for the connectors to be able to reach the tracks of the code plate within closed shifter switch body.

    For the PIN check the drawing in realoem.com with your VIN.
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
    Join Date
    Sep 2008
    Location
    Santa Barbara
    Posts
    3,462
    My Cars
    91 Dinan860 & 91 850 6sp
    There is one guy that still re-manufactures these old 4HP24 transmissions... not "rebuild" but "re-manufacture". He's in LA, Precision European.
    I mention this because, once upon a time, I never gave much thought to those "selector switches". Yet, Herman the German (above) will not sell one of these transmissions without a new one - for good reason. He told me that, before they implemented this policy, over 80% of the "failure" complaints they dealt with were... you guessed it... the Selector Switch. Stuck with me... and fixed more than a few problem cars that "seemed" to need new transmissions (but didn't).
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  11. #11
    Join Date
    Dec 2020
    Location
    New Smyrna Beach, FL
    Posts
    78
    My Cars
    1991 850i
    Though mine is now clean and up and running, I ordered a new one for my newly started collection of BMW 850 parts for future projects........

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