One for the Techies
 

Upgrade early FL 5 speed auto to S mode.

As you will know early FL 5 speed autos did not have the sport setting on the 5 speed. There is quite a bit about re-coding PF and FL boxes to change their shift patterns but little on converting a FL 5 speed with PRND432 to PRNDS.

After a major refit of the Murple thanks to MJ with lots of work done we started talking about this and as she had a TCU from a late model FL S8, we thought we would swap mine out but keep the current shifter to see if it would work.

It does. But there are some oddities. After fitting the replacement TCU the DIS no longer displays the PRND432 or PRNDS! nothing there at all!

We took it out for a run with VCDS attached and the S mode works just as it shoud. In D the car changes up and down as one would expect. In 'TIP' the display comes back on and 5,4,3,2,1, are all displayed and gear changes happen as they should.

However, select 4 on the shifter and, BINGO, VCDS says its in sport mode, the reves change and the box is indeed in Sport mode. Nothing shows on the DIS though.

Select 3 and it all goes horrible wrong! Faults come up, the DIS reports no gear shifts in 'TIP' and I had to stop, turn the engine of and a couple of code were thrown on VCDS to the effect that the F125 switch was reporting an implausible position. As actually it should as there is no shifter position below S (4) on a sport shifter.

So; why is the DIS not showing P,R,N,D,S when in any of those positions?

Thoughts anyone?

Is there some coding, or a software change in the DIS to match the shifter/stick changes?

I am guessing a coding issue of the instrument cluster, when I had my D2 and swapped the radio to an RNS-D I had to code the cluster as the RNS-D was using a different protocol to talk to the cluster.

Maybe MJ could post the coding of the S8 cluster with S Mode and you can compare with yours, but it maybe an adaptation channel that needs altering.

I can't find anything relevant in any of the coding tables or adaptation values for TCU, ECU or cluster. I suspect it may be (but hope its not) firmware changes in the cluster itself.

I think what is happening is that the early FL cluster understands a particular set of CAN messages from the TCU which mean 'show PRND342' and the late FL cluster understands a different set of messages from the later TCU which mean 'show PRNDS'. If that is the case it may be that the early cluster doesn't understand the later messages so doesn't display anything. Without a CAN decoder though, I'm just guessing, and hoping someone else has already solved it!

My thinking was very much along MJs lines, after all why would an earlier cluster have the capability built in to display options that hadn't even been designed?
(Though given car manufacturing lead times they had probably been thought about years before)

very interesting!
my late 2000 3.7 is registered as a sport but has the old display
does this mean that there was a cut off date before which the later display didn't exist ?

yours would be a 3.7 Quattro Sport model (same as my '99 reg car) but thats just a spec thing ie lowered springs by 20mm to match the S8 running height and quattro sport wheels plus recaro sports seats and sports steering wheel etc rather than meaning you get the sports gearbox. that gearbox just came with the later cars

thanks
alles klaar

This has been a popular mod for 10years +

See here:

https://www.audiworld.com/forums/a8-...abled-1754864/

I've never known anyone have an issue like you describe, but its plausible if you have the really early FL (with the old style S badge on the cluster) that perhaps it is too old to cope with the altered PRNDS info ?

Could be. May try swoping in a later FL cluster to check it out.