HOW TO: Access the MFA Secret menu

Discussion in 'Electrical' started by rubjonny, Jul 19, 2010.

  1. rubjonny

    rubjonny Administrator Staff Member Admin

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    To access the magical 'secret' mode, hold the stalk button in on the end of the stalk, then turn the ignition on, off and on again. This works for most if not all MK2 Golf & Scirocco clocks, MK3 Golf and later MK1 cabrio. Earlier MK2 and MK1 tintop clocks do not have this functionality AFAIK. It might be a manufacturer thing for early clocks (only VDO and not motormeter?) or it might have come in when the changeover from clock mounted 1/2 switch to stalk mounted 1/2 switch. Any more details you have would be appreciated :thumbup:

    After stumbling across some excellent information on the internet while researching something entirely different, here is an extended list of the secret functions as found in a US/Canada MFA PDF plus some notes/figures I got from my MK2 16v cluster. Digifiz information has now been added below :)

    MFA switch on position 1 (Check mode):
    Default: Engine code (1)
    1: Country code (2)
    2: Speedometer drive ratio (3)
    3: Upper rev limit (4)
    4: Lower rev limit (4)
    5: Deceleration fuel shut-off pressure (5)
    6: Display test

    MFA switch on position 2 (Measuring mode):
    Default: Test sum of programmed bytes (6)
    1: Intake vacuum (7)
    2: Digital rev counter
    3: Momentary fuel consumption
    4: Signal from speed sensor (8)
    5: Oil temperature (same as normal display)
    6: Ambient temperature (same as normal display)

    1. Country code:
    1 = Germany/ROW
    2 = Canada??
    3 = UK
    4 = USA
    7 = Mexico

    2. Engine code: (For fuel consumption map)
    001 = GU
    002 = RD
    005 = GX
    007 = KR (digifiz)
    008 = EV
    010 = KR (normal MFA cluster 86-87)
    011 = RP
    013 = ?
    026 = PG US/California spec?
    032 = PG
    037 = 9A
    039 = AAA
    107 = KR (normal MFA cluster 87-on)
    111 = PL
    117 = PF
    118 = PB
    123 = PB

    3. Speedometer drive ratio:
    920 = ?
    950 = kmh
    955 = mph
    1080 = Syncro
    3840 = Digifiz (Divide by 4 to get 960)

    4. Upper/lower rev limit: The displayed numerical value must be correct, it is not an indication of the upper and lower overrun fuel cut-off rpm. The upper limit is shown as 7418 for all codes, my KR clocks match up to this. Lower limit:
    9A/KR/AAA/PG = 1175
    PB/PF/PL = 1325
    RP = 1625
    EV/GX = 1925

    5. Deceleration fuel shut-off pressure: The displayed numerical values have no significance but must match:
    9A = 300
    PB = 220
    PF = 300
    PG = 320
    AAA = 220
    KR/PL = 255

    6. Test sum of programmed bytes: Displayed numerical value has no importance for the check.

    7. Intake Vacuum: Some MFA display the intake manifold vacuum in mbar, and others as a decimal numeric value instead. Vacuum readings given in mbar (millibar) do not take into account atmospheric air pressure. The standard reading for atmospheric airpressure is approximately 1000 mbar/1 bar (depending on altitude). Readings less than 1000 mbar indicate vacuum and readings greater than 1000 mbar indicate pressure. See conversion chart below if needed:
    Intake manifold vacuum, mbar in. Hg MFA Display
    100 26.7 15
    200 23.7 55
    300 20.8 90
    400 17.8 121
    500 14.8 148
    600 11.9 172
    700 8.9 193
    800 5.9 211
    900 3.0 228
    1000 0.0 242
    1100 1.5 PSI 255

    8. Signal from speed sensor: Speedometer-drive ratio (from check mode test). Numeric value will change as vehicle is driven.

    With the speed sensor signal display you should see 4 pulses per single rotation of the speedometer pinion. You can poke something suitably square-ish into the hole and spin it by hand if you pull the cable out, I tested this on mine and I get around 6000 pulses per mile. If you multiply the calibration number from the front of a big block mph speedometer 1540 by 4 you get 6160 which matches up nicely to my real world testing. So as a side note the code on the face of a VW speedometer represents the number of speedometer cable/sender rotations per mile or kilometer it expects :)

    Digifiz cluster:
    The procedure for entering the secret menu is the same, mode 1 is check mode, mode 2 is metering mode. When in check mode current function number is shown in the KM display, and output in the clock display. For metering mode the current function number is shown in the clock display, and the output in the MFA display.

    Check mode:
    1: Engine Code (1)
    2: Country code (2)
    3: Speedometer drive ratio (3)
    4: Upper rev limit (4)
    5: Lower rev limit (4)
    6: Deceleration fuel shut-off pressure (5)
    7-11: Internal test values (should display 3, 3, 2 respectively)

    Metering Mode:
    1 Checksum Clo/CErr
    2 Intake vacuum in mbar (7)
    3 Fuel consumption up to 10 kmh in l/h, over that l/100km/h
    4 Signal from speed sensor (8)
    5 Oil temperature
    6 Outside temperature
    7 Display lighting dimming value
    8 Potentiometer value
    9 Photosensor value
    10 Fuel tank capacity
    11 Coolant temperature

    Thanks to Joel Byas/Bromdolf Performance for the Digifiz information, this filled in some of the blanks for the normal MFA secret mode too :thumbup:
     
    Last edited: Oct 12, 2023
    erreesse likes this.
  2. neil kaye Forum Junkie

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  3. cormachalligan96 New Member

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    My clocks dont have the two wee pins that sit either side of the MFA screen.... do i need these to access the MFA menue?

    Thanks
     
  4. rubjonny

    rubjonny Administrator Staff Member Admin

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    thats the clock adjustment buttons, if you dont have them then something isnt right!
     
    Frozenchip likes this.
  5. jonlikescad Forum Member

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    RJ, quick one - if your rev counter is dead will the MFA still read digital RPM or not? I'm guessing no...?
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    depends why its dead! if there is a wire fault then digital display will not work, same if there is damage between clock pin and mfa pcb. if the problem is with the rev counter itself then its possible the digital display will work even if needle doesnt
     
  7. Miguel Duarte New Member

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    Hi, great post!

    About the deceleration fuel shut-off pressure, you say the displayed numerical values have no significance but must match. In my case (golf mk2 from 1989, KR engine) that dosen't happen, i get a reading of 74. The fuel consuption readings on my cluster are super low, can this problem be because of this?
    Everything is alright except the deceleration fuel shut-off pressure value.
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    What I assume its for is on over-run while decelerating this vacuum value set is where the cluster ignores vac input for the mpg calculation and/or it switches to a different calculation table. I see similar on our MK4 golf the mpg goes to --- when coasting along no throttle.

    Dont think there is anything you can actually do about this, I take it the intake vacuum position reads correct?
     
  9. Miguel Duarte New Member

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    I think so, i unplugged the vac hose and the display reads about 230, when i plug the hose again and turn on the engine it reads about 60
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    yep that seems about right. does the average speed and distance settings agree with the mechanical oddometer?
     
  11. Miguel Duarte New Member

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    Yes the mechanical oddometer and the digital rev counter are working fine
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    no I mean the average speed and distance settings on the MFA, in particular the distance one does it agree with the mecahnical display. as if the vehicle speed isnt read correctly this affects the mpg calculation
     
  13. Miguel Duarte New Member

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    Is it normal the signal from speed sensor displayed on the mfa not being "0" when the car is stopped?
    Right now displays 3519 and goes climbing with the car moves. This value never resets when i turn the key off
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

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    Yep normal, the secret mode for this is just a sensor pulse counter, not speed measurement. You should get around 6000 pulses per mile
     
  15. rubjonny

    rubjonny Administrator Staff Member Admin

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    For km multiply the 4 digit code on the front of the Speedo by 4, that gives you the pulse count per km :)
     
  16. Miguel Duarte New Member

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    Just finished testing that, i got a speedometer in kms with "950" writed in the front. Giving me 3800 pulses per km, after testing i got values betwin 3700 and 3900 so i guess the speed sensor is working fine
     
  17. rubjonny

    rubjonny Administrator Staff Member Admin

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    yep that all seems spot on, so it does seem like you have an internal cluster error but seems unlikely to me... did this error just happen all of a sudden or has it always done it? you could try a cluster reset by pulling out the clock fuse for 30 seconds if its just happened all of a sudden
     
  18. Miguel Duarte New Member

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    This error started when all the vacuum lines were changed by new ones. But all the hoses are connected without any leaks...
    Did the reset, the average fuel consumption starts counting at 99.9 liters per km but when i keep driving it goes down to very low numbers again (1 or 2 liters per km) and stays there
     
  19. rubjonny

    rubjonny Administrator Staff Member Admin

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    where did you connect the MFA vacuum hose engine bay side and are you sure its not split or disconnected behind the cluster
     
  20. Miguel Duarte New Member

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    The MFA vacuum hose is connected to a T-fiting with one end going to the vacuum tank and the other going to the valves next to the intake boot.
    I tried running the cluster with the vacuum line disconnected and i had better results (with car stopped got this readings on the secret menu):

    Current fuel consumption:
    [​IMG]
    [​IMG]
    https://www.dropbox.com/s/9f26v249xrnzecx/FC with vac.jpg?dl=0
    https://www.dropbox.com/s/qkpsvbv6gg4qtnu/Fc Without vac.jpg?dl=0

    Intake vacuum:
    [​IMG]
    [​IMG]
    https://www.dropbox.com/s/xi8i63acfncxicd/Vp with vac.jpg?dl=0
    https://www.dropbox.com/s/2jqcupxuti3nsvt/VP without vac.jpg?dl=0

    When i rev it up a bit:
    https://www.dropbox.com/s/6dnpeh0up88mo4w/FC rev with vac.jpg?dl=0
    https://www.dropbox.com/s/wny6y3ll2gnnv88/Fc rev without vac.jpg?dl=0
    [​IMG]
    [​IMG]
     

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