HOW TO: Access the MFA Secret menu

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

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

 

thats the clock adjustment buttons, if you dont have them then something isnt right!

 

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

 

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?

 

yep that seems about right. does the average speed and distance settings agree with the mechanical oddometer?

 

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

 

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

 

For km multiply the 4 digit code on the front of the Speedo by 4, that gives you the pulse count per km

 

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

 

where did you connect the MFA vacuum hose engine bay side and are you sure its not split or disconnected behind the cluster