CITROËN DS3 R3 Max System User's Manual page 13

Beside the electrical diagnostic done (invalid if the voltage value is out of thresholds set), the gearbox automate
is based on this measurement, actually from the barrel position regulation, all the gear changes will depend on
it (engaged, disengaged). Therefore, the way to set it correctly (if you have to remove the sensor) will be as
follow:
- Connect the sensor
- Make sure that the gearbox is mechanically in neutral
- Position the sensor by checking the current barrel value on the dashboard (first mechanic page), which has
to be 1000mV ±5mV.
A mark is on the side, which should be set up upward. If the sensor is fitted upside down,
the display will show '4' instead of '0'.
Few time in this document, "Neutral position of the gearbox" idea has been raised. You
must know that if you do not pay enough attention to potentiometer calibration,
the quality of the entire gearshift system will be modified, as well as the durability of the gearbox components.
Barrel position
If the system detects an unknown position for more than a 10ms, then
the default gear "5" will be displayed. The driver will then be allowed
to downshift or upshift depending on the situation.
Unknown position displayed as 'F' by the system.
System User Guide - 03.12.14
2. Driver System Overview
4. Gearbox Management
13