F125 switch versions

[MikkiJayne]

So from that can we surmise that mine was getting a completely invalid code from the switch since it displayed nothing? PRNDS was displayed with nothing highlighted with the shifter in R, and would only show R on the display when pushed to just the right spot.

[HPsauce]

That's my best guess now, and one reason why I did the test today.
My surmise above was probably wrong:

Originally Posted by HPsauce

MJs suspect F125 pictured in her Workshop thread, may well have been giving a 1100 code (between R and... N or P) when R was selected (normally 0100).

But remind me how it behaved. I recall you said the reversing light was on (not a surprise, separate circuit) but had it selected Reverse gear, or not until indicated on the display and the TCU commanded the valve body?

[MikkiJayne]

Originally Posted by HPsauce

But remind me how it behaved. I recall you said the reversing light was on (not a surprise, separate circuit) but had it selected Reverse gear, or not until indicated on the display and the TCU commanded the valve body?

It wouldn't select R unless the shifter was held in between P and R in an extremely precise position (within a mm or two). I think the necessary sprung contact was only making a connection right on the edge of the base contact, so any movement either way and it failed and dropped out of gear. R on the cluster was coincident with it being in gear, which makes sense as the TCU will send it a CAN message.

Having cleaned it up and put it back in, I was checking the shifter alignment yesterday using VCDS. Between P & R and R & N the TCU shows 'Z1' and between N and D it shows 'Z2' so those intermediate contacts definitely tell it something different. Presumably its so it can prepare for what is coming next - it apparently can't tell direction, since it can be put in to Z2 from D, and then put straight back in D, but I guess it uses the Z positions to prepare the gearbox for what may come next.

I didn't get the binary code for Z, but that can probably be worked out from the contacts, or observing VCDS again.

[HPsauce]

Originally Posted by MikkiJayne

Having cleaned it up and put it back in, I was checking the shifter alignment yesterday using VCDS. Between P & R and R & N the TCU shows 'Z1' and between N and D it shows 'Z2' so those intermediate contacts definitely tell it something different. Presumably its so it can prepare for what is coming next - it apparently can't tell direction, since it can be put in to Z2 from D, and then put straight back in D, but I guess it uses the Z positions to prepare the gearbox for what may come next.

I didn't get the binary code for Z, but that can probably be worked out from the contacts, or observing VCDS again.

Excellent research. I think that's consistent with what I worked out and documented in post #16 above. Z1 = 1100, Z2 = 1010.
There should be another code for between D and 4/S. And a 4th code for 4-3 and 3-2 if have that available.

So we do now know that those intermediate positions exist and are recognised by the TCU, though not if it does anything (or what) as a result.
This could be the basis of another useful diagnostics test on the F125, moving the shifter slowly and monitoring the TCU.
Where exactly in VCDS do you find those codes?

[MikkiJayne]

Originally Posted by HPsauce

Excellent research. I think that's consistent with what I worked out and documented in post #16 above. Z1 = 1100, Z2 = 1010.
There should be another code for between D and 4/S. And a 4th code for 4-3 and 3-2 if have that available.

So we do now know that those intermediate positions exist and are recognised by the TCU, though not if it does anything (or what) as a result.
This could be the basis of another useful diagnostics test on the F125, moving the shifter slowly and monitoring the TCU.
Where exactly in VCDS do you find those codes?

I couldn't get it to show anything for that - it just went straight from one to the other.

Its in measuring blocks. I can't remember which one but not very far in. Scroll through and you'll see it.

[HPsauce]

Automatic Transmission (2), Measuring Block 4 and it also shows the binary 4-bit codes on the F125, exactly as I had worked out in fact.
There's a higher block (11?) that shows some of that data (and Tiptronic IIRC) but block 4 is best.

My car is of course exactly the same, only Z1 and Z2, no code between D and S.

BUT a really interesting observation! When VCDS was showing Z1 or Z2 the DIS was no longer highlighting a selector position.
It was still showing PRNDS but no red highlight until the stick moved slightly and the F125 showed a standard position.
MJ, is this what yours was doing when you struggled to get reverse or was PRNDS missing?

Edit, I think you did have PRNDS displayed, so that could indeed have been a Z1 or Z2, not a totally invalid code, just "in transit":

Originally Posted by MikkiJayne

So from that can we surmise that mine was getting a completely invalid code from the switch since it displayed nothing? PRNDS was displayed with nothing highlighted with the shifter in R, and would only show R on the display when pushed to just the right spot.

And in fact my initial guess may well have been correct, with a Z1 code being read:

Originally Posted by HPsauce

I reckon MJs suspect F125 pictured in her Workshop thread, may well have been giving a 1100 code (between R and... N or P) when R was selected (normally 0100).
This could have been due to shorting of the track for pin 2 to its contacts, while still having the reversing lights on.

[MikkiJayne]

Originally Posted by HPsauce

BUT a really interesting observation! When VCDS was showing Z1 or Z2 the DIS was no longer highlighting a selector position.
It was still showing PRNDS but no red highlight until the stick moved slightly and the F125 showed a standard position.
MJ, is this what yours was doing when you struggled to get reverse or was PRNDS missing?

Edit, I think you did have PRNDS displayed, so that could indeed have been a Z1 or Z2, not a totally invalid code, just "in transit":


And in fact my initial guess may well have been correct, with a Z1 code being read:

Yep thats exactly it. It must have been seeing Z1, so not throwing any errors. Only in that one specific position did it get R.