Changed the Accumulator and flushed out the old oil today.
Thought it might be a small leak behind the gear engagement sensor,
so removed this to se if there was a faulty gasket underneath.
I didn't pay attention to the position the "axle" underneath had,
and so when refitting it, I might not have sat it on correctly.
(it's a bit like a tps sensor, only the axle isn't spring tensioned)
Have had a search,
but can't fint any threads regadring exactly this problem.
Must be a way to "zero in" both the axle and sensor,
but I DON'T KNOW HOW
Now I get Selespeed warning light,
and "P1741 - Engagement Sensor - Voltage to high" fault when connecting to FIAT ECU Scan
The unit looks like this,
and sits on top of the hydraulic unit.