geek question - tiptronic on-demand change
05-23-2006, 10:46 PM
#1
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geek question - tiptronic on-demand change
the later model tip's allowed on-demand gear changes using the tip buttons on the steering wheel, regardless of whether the tranny was in tip mode or not. the normal "d" mode resets itself after a few seconds in tip mode.
i've looked at the wiring diagrams and can see how to do it. you will require this sequence of steps:
1) tip button hit
2) initiate tip mode using relay
3) initiate tip gear toggle (up or down)
4) initiate tip time out using relay
5) either another tip gear toggle or time-out
6) time-out, reset tip mode
has anyone gone any further than the above? if so, share!
if not, is there interest in developing a running modification for those interested to allow this to happen. i'm thinking source and supply of the relay, wiring modifications and instructions for the re-fit.
if there is interst, i'll share on this thread how i think it can be done, and we can take it from there...
comments?
i've looked at the wiring diagrams and can see how to do it. you will require this sequence of steps:
1) tip button hit
2) initiate tip mode using relay
3) initiate tip gear toggle (up or down)
4) initiate tip time out using relay
5) either another tip gear toggle or time-out
6) time-out, reset tip mode
has anyone gone any further than the above? if so, share!
if not, is there interest in developing a running modification for those interested to allow this to happen. i'm thinking source and supply of the relay, wiring modifications and instructions for the re-fit.
if there is interst, i'll share on this thread how i think it can be done, and we can take it from there...
comments?
05-24-2006, 07:04 PM
#3
Is there anyone whose steering wheel Tip buttons work with the gear lever in D ...
who can report the part number and coding of their transmission control module? (VAG-COM will show them when you connect to the transmission control module.)
With the stock wiring, this feature could be (and probably was) implemented in TCM software. I'm curious if it can be enabled in other cars via a TCM coding or adaptation change.
Skiwi, if you make an adapter box to enable the same feature, it may need an interlock to prevent the Tip switch relay from activating with the gear lever in other than D -- if such normally impossible combinations put the transmission into emergency running mode.
Tom
With the stock wiring, this feature could be (and probably was) implemented in TCM software. I'm curious if it can be enabled in other cars via a TCM coding or adaptation change.
Skiwi, if you make an adapter box to enable the same feature, it may need an interlock to prevent the Tip switch relay from activating with the gear lever in other than D -- if such normally impossible combinations put the transmission into emergency running mode.
Tom
05-24-2006, 11:30 PM
#4
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good point
i've been focusing on the 4 outputs of the tip steering wheel and their interface to the tiptronic switch (l96), but you're right i need to understand that the tranny is in "d" mode 1st. i'll have to think about that some, and perhaps measure some outputs. the tranmission range switch (f125) knows when it is in "d" mode, as it outputs this to the control module (j217). as it is the tcm that controls the interlocks, it shouldn't be too hard...
the interlocks are the "t10/5" (blue) and "t10b/7" (yellow) connectors in the plenium chamber which i have to take some measurements from.
one thing i am struggling with is that there is a blocking diode on the 3rd output from the tip switch to the tcm which controls the tip switch itself (i.e. in tip or not). i'm not sure why the diode is there...
for those interested i am talking about the wiring diagrams for group 20 (page 7) and 23, page 3.
the interlocks are the "t10/5" (blue) and "t10b/7" (yellow) connectors in the plenium chamber which i have to take some measurements from.
one thing i am struggling with is that there is a blocking diode on the 3rd output from the tip switch to the tcm which controls the tip switch itself (i.e. in tip or not). i'm not sure why the diode is there...
for those interested i am talking about the wiring diagrams for group 20 (page 7) and 23, page 3.
05-25-2006, 08:54 AM
#5
A dark corner of A8 electrotrivia -- the purpose of the blocking diode
The diode first appears on the 2002 wiring diagram. Why wasn't it necessary before? Turns out it was, sometimes -- it's a patch. Here's the circumstantial evidence:
Technical Bulletin 37-02-01 for 2000-2002 cars says to replace the TCM and shifter wiring harness (using a specified part number, presumably containing the diode) if the transmission goes into emergency running mode and the +/- lights on the shifter stay lit after shifting to D from Tip with the headlights and ignition on. It says the P1744 (Tiptronic switch recognition circuit, short to ground) may also be stored.
The symptoms in the bulletin -- the +/- stay lit up after shifting out of tip, and the TCM is to be replaced -- indicate that the Tiptronic switch input has become damaged and has become an output, continuing to provide a ground which keeps the +/- lights (L96 in the wiring diagram) on.
That fact that the bulletin requires the headlights to be on when reproducing the problem suggests that it is triggered by positive current flowing through the +/- lights into the TCM when the switch is not in Tip. Put the diode in and this can't happen any more -- the Tip recognition sees only ground from the switch or nothing, no more positive voltage through the lights.
(On my pre-diode 2001, turning on the headlights with the key off and the lever in P causes the +/- lights to illuminate to almost full brightness. Current is flowing through the lights into the TCM's Tip switch input, and doing who knows what. That can't be good for an input which is evidently fragile when connected to positive voltage.)
Tom
Technical Bulletin 37-02-01 for 2000-2002 cars says to replace the TCM and shifter wiring harness (using a specified part number, presumably containing the diode) if the transmission goes into emergency running mode and the +/- lights on the shifter stay lit after shifting to D from Tip with the headlights and ignition on. It says the P1744 (Tiptronic switch recognition circuit, short to ground) may also be stored.
The symptoms in the bulletin -- the +/- stay lit up after shifting out of tip, and the TCM is to be replaced -- indicate that the Tiptronic switch input has become damaged and has become an output, continuing to provide a ground which keeps the +/- lights (L96 in the wiring diagram) on.
That fact that the bulletin requires the headlights to be on when reproducing the problem suggests that it is triggered by positive current flowing through the +/- lights into the TCM when the switch is not in Tip. Put the diode in and this can't happen any more -- the Tip recognition sees only ground from the switch or nothing, no more positive voltage through the lights.
(On my pre-diode 2001, turning on the headlights with the key off and the lever in P causes the +/- lights to illuminate to almost full brightness. Current is flowing through the lights into the TCM's Tip switch input, and doing who knows what. That can't be good for an input which is evidently fragile when connected to positive voltage.)
Tom
05-26-2006, 01:04 PM
#6
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good informaiton thanks
i did some testing last night and the 2 feeds from the tranny tip switch activate as expected. however, although the wiring diagrams show that the steering wheel tip buttons also connected to these points (in the yellow and blue connectors in the plenum), they do not activate. it looks as though i might have to trace these from the dash. worst case they feed through the dash controller...
05-26-2006, 07:52 PM
#7
The problem with the tip switch is, that it is not a independent closed circuit.
It shorts the signal from the TCU to the ground, so if there is any interference or bad feedback from other accessories, it can go back to the TCU. The diode will allow the current flow one way only.
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05-26-2006, 10:49 PM
#8
Hmm. Let us know when you find out how it's really wired
I still wonder if it would be easier to track down a car on which this feature already works, then see if there are differences in the TCM coding or adaptation (which might work elsewhere with no wiring changes) or TCM part number.
Tom
Tom