What's in the workshop this week?

[MikkiJayne]

The gearbox mechanically only sees PRND if memory serves (possibly one position after D - I'll check later). [edit - this bit is incorrect but left here for context later] The cable stops moving after that, and the other selections are done in the shifter mechanism which is connected directly to the TCU, so S, 432, and tip are all just software in the TCU. [/edit] The TCU definitely uses the F125 to know what mechanical mode the gearbox is in. There's no other sensing circuitry. Presumably ZF put it there as part of the gearbox design, and then left the selector mechanism and the actual software up to the OEMs.

This is why you can get S mode in an FL1 by changing over the TCU, although changing the shifter top is also important as if you put an S ecu in to 3 or 2 it gets quite cross! The only issue I've found so far with that upgrade is that the cluster gets a tad confused and tends not to display the gear selection at all. I think the later TCU sends a different set of messages for PRNDS compared to the early one for PRNDS432. I need to swap in an FL2 cluster which I'm sure will solve it.