The sender unit is positioned on the gearbox just above the drive shaft on the drivers side - it is held in place by one bolt and will take about 10 minutes to replace. A replacement will be about £80 from a fiat dealer, but I believe the peugeot boxer uses an identical part for about half that price. Be wary of oil leaking from the gearbox when you remove the old one. This can be avoided by jacking up the drivers side front wheel so that the oil runs to the oposite side of the gearbox.
mjt42, March 2011
