A non-volatile memory stores values defining a released position or a depressed position of a clutch pedal. A potentiometer mechanically linked to the clutch pedal produces an output signal whose value or magnitude represents the current position of the clutch pedal. When power is turned on, first and second end limit values which electrically define the depressed and released positions of the clutch pedal are read from the memory, a constant value is added to the first end limit value and subtracted from the second. Thereafter, each time the output signal is sensed for control purposes, the output signal is compared with the end limit values. If the output signal is less than the first end limit value it replaces that value in the memory and if the output signal is greater than the second end limit value it replaces that value. The sensor is thus calibrated in a manner transparent to the operator each time the system samples the sensor output signal for control purposes. When either end limit value is changed, threshold values representing specified positions of the clutch pedal relative to its released or depressed position are recalculated and stored for subsequent use as control values.